When he played live that was his setting.
You'll never get the exact sounds he has on record, ever. Unless you have thousands of dollars to spend on equipment. What you're hearing on the recordings is loads of different guitars going through several different amps, with several different pedals, and several different layers of guitar tracks, which then all got sent through the magical mixing desk of Butch Vig.
If you want a basic Nirvana-esque setup you're going to need a medium wattage British voiced tube amp that breaks up at about medium volumes, but still has enough headroom to play cleanly at fair volumes. Set the DS 1 with the level and drive maxed, tone at wherever you think is best. Set the amp so that it's on the verge of distortion but will stay clean if you play softly or roll back your volume knob, this will be your clean tone. Now since your amp is on the verge of distortion when you hit on your DS-1 you're going to get lots and lots of thick creamy tube saturation--the sound you're probably looking for.
Also you'll probably want to change the pickups on that guitar for ones that are a little hotter, this will help hit the front end of a tube amp better, and buy a clone chorus or polychorus or both.
