My new bass project will have two MM pickups (I haven't decided on which ones yet). I'm trying not to spend insane amounts of money here, but I do like a little of that Stingray "zing". I'm thinking about starting off cheap with a couple of GFS Alnico pickups with just a tone control and maybe upgrade with a Bartolini NTBT, or an MM preamp clone, if I need more tone shaping possibilities. Series/parallel/single switches will also be installed. I know MMs are usually paired with onboard preamps, but how will they sound with a passive tone control?
Two MM style pups in passive should sound fine (think G&L). There is no electrical reason they need a preamp any more than any other style pup.