|Josh Pardes||Re: adding one or two more single coil pickups|
There are a couple of things that need to be checked before you do it. Firstly, to cancel noise, the magnets in your existing bridge pickup need to have the opposite polarity of the pickup you want to install. You can check this by using a cheap compass. Hold it about 1" away from the pup. If the north arrow points to it, the magnets are south side up, and vice versa if the north arrow goes the opposite direction. If your birdge is south up, then you need to find a pup with north up, or vice versa. Secondly, if you want it to have a fatter, higher gain sound with more midrange you need to wire the pickups in series. To do this, you need to leave the hot wire on your bridge hooked up to the switch, desolder it's ground wire and connect it to the hot wire of the new pickup then solder the new pickup's ground wire to ground. To do a coil tap, all you need to do is ground the connection between the two pickups (where existing pickup's ground connects to new pickups hot). This will short out the new one and leave you with the original bridge sound. There is a 50% chance that you will have to reverse the wires on the new pickup (i.e. old pickup ground to new pickup ground wire, new pickup hot wire to ground point). This is because the new pickup may not be reverse wound which would cause the two pickups to be out of phase. You will be able to hear it immediately if they are. It will sound thin and trebley if they are out of phase. Additionally, you could wire them in parallel, however it will not sound at all like a traditional humbucker. For best noise cancellation try to use a pickup that has roughly the same resistance as your bridge. You can check that with a volt/ohm meter. No big deal if not. Most strat pickups are around 6k anyway. Let me know if you need any more details. Good luck.