Guitar Wiring Explored – Switches Part 2
In the last two articles we looked at switches, and then four-conductor humbuckers and some things you can do with them. This time around, we’re going to look at some new types of switch, and see how we can use those to access even more tones from a humbucker.
DPDT on-on switch
The switch we looked at last time looks like this:
It’s a double-pole, double-throw switch, and it has two positions. This type is called an “on-on” switch, because a connection is made in both of these positions. This is the type of switch built into push/pull pots. It’s also the most commonly-used type of mini toggle switch. You can use it as a simple on/off switch by only using two of the poles, or you can use more connections to create more complex switching systems.
DPDT on-off-on switch
This switch has three positions. It’s not available as a push/pull pot, only as a toggle switch. The toggle switch stops in the middle to give us the extra position. The connections made with the switch in each position look like this:
You can see that in the middle, no connections are made at all, while on the two extremes of the switch, the connections are made in the same way as an on-on switch. Therefore, this switch is called an on-off-on switch. A good example of use for this switch would be to control which coils are active in a four-conductor humbucker. Here’s a diagram:
We’ve taken the red and white wires from the humbucker and connected them to the center terminal on one of the throws of the switch. When the switch is in the middle position, these wires will not be connected to anything else, so the pickup will act in full humbucker mode.
When the switch is in the “up” position, you’ll see that these two wires will be grounded. This gives us the same coil split we achieved with a simple toggle switch in the last article – giving us the slug coil active and the screw coil bypassed. Note that of course the green and bare wires from the pickup can be grounded anywhere – but given that all the other wires from the pickup are going to the switch, it’s convenient to bring those two in here as well.
However, when the switch is in the “down” position, you’ll see that those two wires are connected to the hot output of the pickup. What this does is equalize the voltage between the start and end of the slug coil – meaning that now we have an active screw coil and an inactive slug coil. So this switch gives us the option between both coils active, or either of the coils in isolation. This opens up some slightly different tones in a normal humbucker, but with a P-Rails it really comes into its own. In that pickup, the switch we have wired here allows us to select between the P-Rails’ three main modes: P90, single-coil rail, or full humbucker.
Because we have only used one of the two throws on the switch, we could use the other three contacts with another humbucker to control two humbuckers in the same way with one switch.
Next time we’ll be looking at the last kind of toggle switch and seeing what kind of options it gives us. Any questions so far?
Here’s a video demonstrating the sounds available from the P-Rails.