SC-2/ASAT 4-Way Switching with revised Tone Control wiring diagram
What you get is one additional connection (when using a 4-way switch)...which is the neck + the bridge pickup in series in phase (as opposed to the typical parallel in-phase connection) you get between two pickups. At this point I've lost track of all the times I've done this for myself and others...great, great, great mod.
What does the serial connection get you?...well, in simple terms it gets you the sum of the outputs of both pickups at the expense of a narrower and lower frequency response. To you ears you hear a bunch more volume, a bunch more midrange and a bit less treble content. Your amp will provide a dirtier tone for sure compared to the other three settings. It is almost like a sound from a completely different guitar...and I love it. No need to stomp on a pedal...this setting gives you a searing hot lead tone in spades...
Now, check this out...back off your tone control and it is jazzer city...very surprisingly great sounding for sure...great stuff!!!
It is very basic to follow...anybody can handle this mod with great ease.