I use a Humphrey Audio Badder Bass Monkey!!! Its a MODDED Digitech Bad monkey Tube Overdrive. Can get 'em on US Ebay-approx $90 !!!
I used to use a black Big Muff(russian one) & I still use that for over the top sustain........but the Badder BM Is a BEAUTY!!!!!! Sounds like a tube amp on OD!! My fave thing about it is it's ease of use! Where the Big Muff- you touch the sustain or gain & the volume goes thru the roof, so U gotta compensate for that..... & so on......
The Badder Bass Monkey- turn up gain & U get more OD -NOT VOLUME!!!! Turn up VOLUME & U get more VOLUME!!!!!
It has BASS & TREBLE controls also & U lose NO BASS/bottom end, so for overdrive- like the big muff sounding-ragged & rough, but easy to control & great for tube OD sounds!
ONE flaw-IMO- with drive(gain) OFF, it still gives a fair bit of OD(not a lot) I'd personally like there to be virtually NONE in the off pos.
Still- a GREAT pedal -especially at the $$$$$