There are numerous musical applications to this mod. Whereas a volume knob takes more time and effort to turn down, the switch produces a complete and immediate cut, so you can use it for interesting effects in your playing. For example, Eddie Van Halen employed this approach on the end of the solo on "You Really Got Me" on the band's first album (around 1:50 into the track).
Note that in this case, rather than using a true "kill" switch as is described on this page, he toggled his regular 3-way pickup selector between the bridge pickup and the absent neck position. He routinely took out his neck pickup (or at least didn't bother to wire it up; see the Frankenstrat, for example), but you can accomplish the same sound by simply turning the volume on the neck pickup all the way down provided it has a separate control (e.g., as on a Les Paul).
The current master of the kill switch is the guitarist Buckethead, who employs one extensively and inventively in his (often) avant garde playing. For example, chopping up a droning distorted chord by inserting breaks via the kill switch can make it sound as though the guitar is being strummed, something that otherwise wouldn't really be possible without the kill switch.
|Pop goes the input
Cutting the signal almost always results in a popping sound on a clean, non-distorted tone. The reason is that the wave is cut from whatever amplitude it has (see the white arrow in the picture). However, if you are distorting the signal, it will clip it anyway, so this won't be nearly as noticeable. There's nothing wrong with the wiring; it's just the physics of the situation. This mod sounds best with a heavy, overdriven signal anyway, so it works just fine for most players.
Buckethead uses a momentary switch to accomplish the same thing as you might with a toggle, only the effect lasts for only as long as you press the switch. This has the advantage of allowing you to alternate between "off" and "on" even faster than via a typical "throw" type toggle switch.
There are two different types of momentary switches out there, so you need to know which you have in order to wire the mod correctly. If you don't, then the signal will be cut when you aren't touching the switch and will only pass when you press it. That would make for an awkward playing style for most pieces.
The nomenclature for these switches is as follows.N.O. contacts = Normally Open contacts = The circuit is open (i.e., "Off") when the button isn't touched. When you touch it, you make a connection between the two contacts.(Thanks to KS for pointing out the terminology.)
N.C. contacts = Normally Closed contacts = The circuit is closed (i.e., "On") when the button isn't touched. When you touch it, you break the signal.
This is modification is so simple to accomplish that I didn't even bother to draw a diagram for this page, but site reader KS sent two of the following images, then I altered his design to give another option.
This is how your output jack probably looks. Just two wires to two lugs. (If you have a preamp or active pickups, then there's maybe a third. Concentrate on the ones not connected to the battery, obviously.)
Using an N.O. switch
One approach is to use the switch to short the circuit, creating a loop from input to output that bypasses everything in the guitar.
Using an N.C. switch
With this switch you create a break in the line.
Note: I had a report from site reader Max that this version just results in a hum rather than silence when pressed. If that's the case, break the "hot" (or "power") wire instead.
Ideally, the best place to insert the switch into the circuit is just before the output jack. Some other places will certainly work just as well, but this is the safest approach so you don't end up cutting, say, your neck pickup but leaving the bridge pickup connected. That might be interesting in some ways, but then you wouldn't have the freedom to cut the signal in all positions.
However, if you have some difficulty wiring it to the jack for reasons of space (i.e., too many wires in too confined an area), then an alternative possibility is to go from the volume knob lug (either going into or out of the pot) to the ground using a momentary N.O. switch. It's an equivalent circuit, just different arrangement physically.
Like I said above, electronically there is no difference between a kill switch and a standby switch. They both cut the signal. However, the terms grew out of the fact that a standby switch is more like the "standby" switch on some tube amps. In other words, it's something to cut the signal while the rest of your gear is turned on, warmed-up and waiting. By contrast, the kill switch is a momentary interruption of the signal for more immediate musical purposes. Don't worry about the semantics; only the music matters in the end. Think about how you'll use a mod, then implement what you want as you need it.