Introduction to DIY Guitar Effects Pedals: A Simple Killswitch
An Introduction to DIY Guitar Effects
If you're interested in building your own DIY guitar effects pedals, it is often obviously easier to start off with a simpler build, and one of the simplest possible builds is a passive killswitch pedal. A passive pedal doesn't require a power source (like a battery). In case you don't know what a killswitch is, it is a momentary pushbutton switch that cuts the signal to a ground for as long as the switch is held down. If you had a hard time following that description, you are definitely reading the right article. I'll walk you through a simple building process and introduce to to the basics of pedal building. Now let's actually learn something.
Image from Tube-Town.net
We'll Be Using Some Pretty Big Words, Here's Your Dictionary for This Lesson.
- Pushbutton switch - This is the switch you operate with your foot. There are many different kinds of switches, such as SPST, DPDT, and 3DPT, that you needn't worry about at this time. We are only working with one type of switch in this pedal. Here's a great article to help you understand switches!
- Momentary switch - this is a switch that stays on only while you have it pressed.
- SPST switch - this is a switch that is either completing a circuit (on), or shorting it (off). It does not switch between two different circuits. This is the type of switch that we will be working with today.
- Normally closed ( N.C.) or normally open (N.O.) - these are terms used to describe a SPST momentary switch. A momentary switch that is N.C. means that it normally allows the circuit to flow freely. A momentary switch that is N.O. means that it normally shorts the circuit. When depressed, the switch will either open (N.C.) or close (N.O.) the circuit. Understanding this is probably the hardest part of this project.
- Hot and ground wire - the hot wire is what will carry the signal in the pedal. The ground prevents hum and other noises. Both are essential in every circuit.
Here's What You'll Need to Make This Happen:
- 3 Lengths of Electrical Hookup Wire (one long, two half the size of the long)
- 1 SPST Momentary N.C. switch
- 2 Female 1/4" Mono Input Jacks
- Wire Cutters
- Wire Strippers
Will Make It Easier
- Needle Nose Pliers (optional)
- Enclosure (optional)
- Soldering Iron (Highly Recommended)
- Solder (Needed for Soldering)
Everything You Need
How It Works
A Light of Understanding...
Chances are you've replaced a light switch before. A killswitch is like the light switch for your guitar. As long as your foot is pushing down on this thing, the signal will be cut off and there will be nothing coming out of your amp, except maybe a bit of hum if you're using built in amp distortion. As soon as you release your foot, the signal will flow freely, and your setup will behave normally. How does this happen? It's pretty basic. Like a light switch, you are either breaking or completing the circuit depending on what position the switch is in.
All that's happening when the signal is cut is the hot wire is being shorted to a ground, basically breaking the circuit. And 7th grade science class tells us that when a circuit is broken, it doesn't work.
So there should be two tabs on your input jacks. As illustrated by the diagram to the right, one tab is a hot (carrying the signal) and one is a ground (keeping the pedal from making noise), which is also called the sleeve. Now it's time to start building, there are many different ways to make a killswitch pedal, but I am showing you what I think is the easiest.
image from guitarnucleus.com
Putting It Together
Finally Getting it to Work!
- Take the long piece of hookup wire and strip the coating off of the ends so the wire underneath is exposed. Then take that piece of wire, and connect the two ground tabs on the input jacks. You can either crimp the wire, or solder it, your choice (it will be more secure soldered, and will create less noise; it may unconnect if crimped).
- Take the two shorter pieces of hookup wire, and again, strip the ends of them. Then take one length of wire, and connect one of the hot tabs to one lug (joint) on the momentary switch. Then take the other length of wire, and attach the other hot tab to the other lug.
- If you're confused, please refer to the circuit diagram in the pictures. Here are the symbols for a schematic (in case you can't read it).
- Now test your pedal. If it works as expected and cuts out the signal when you press the button, then congratulations! You did everything right and completed your first pedal! If it didn't work, then you may need to troubleshoot a bit.
Have Issues? Let's Fix 'em!
Here are a couple common issues that I have found, and mistakes I have made:
- The hookup wire is broken in some way, this could be either underneath the wire's shielding or exposed. Tug on the exposed wire and move the wire around to make sure it's not internally fractured.
- The connections are not complete, this possible even if you soldered your connections. If you crimped your connections, make sure they are tight and won't fall off easily (or at all). If you soldered, make sure there are no bubbles or extra solder, and remove the extra with a solder braid.
- A hot tab is connected to a ground tab. This is a mistake that I made. It results in significant volume and tone loss. Simply double check your tab connections.
- Something conductive is touching something in the circuit, this could short the circuit.
- Your momentary switch is N.O. instead of N.C., this will result in the signal passing through when the switch is depressed. Double check the type of switch you got
- The switch isn't momentary, self explanatory. Again, double check the type of switch.
Always Room for Imrovement
- Add an LED Indicator - this would require an entirely different switch along with a battery, and a whole new circuit. This will be easier later.
If you decide to do this, this site will help you a lot.
- Add a cutoff switch - by adding a latching (NON-momentary) SPST switch right after or before the momentary can give you a cutoff switch, which is useful during long breaks or to change guitars without a lot, or any, noise. This can just be placed on the hot wire, adjacent to the momentary.
- Reduce the pop when pressing the switch - if you add resistors before and after the momentary switch, it will reduce the popping noise that is noticeable if you use the killswitch clean. Please refer to this short tutorial to learn how to do that.
Killswitch with LED
Some Great Pedal Building Resources!
- Article on getting Started with Pedal Building
This is a great article from Beavis Audio on getting started with guitar pedals. It covers numerous topics and is very helpful.
- DIY Stompboxes Forum
A great forum full of knowledgeable people who are happy to answer your questions! It's a great place to go if you're stuck on ANY project!
This article is all about switches; the different kinds, what they do, where they go, and how to use them.
- The Stutter Pedal
Another in depth explanation of a killswitch pedal.
- Schematic Symbols
A great resource for looking up schematic symbols.
- Booster: How It Works
This may be a bit advanced, but if you are looking to take the next step this is a great way to go! This graphic walks you through how a simple booster works and what all the components do. At first it may look daunting, but you will understand it af
- From Schematic to Reality
This article gently guides you through decoding a schematic on your own.
- Stocking Parts
This is a great article on what parts you should stock up on to jump from one project to the next easily. It's a great resource to understand what's essential.