Intro: Guitar Amp Footswitch
Recently, I acquired this guitar amp to use it when I want to practise but don't want to use my bigger rig. I'm planning on revamping it. The previous owner lost the footswitch so I thought I would make one just for the fun of making it instead of buying a new one. I will make this Instructable so that everyone can custom build one and understand each steps of this process, thus explaining in details how to choose the right components.
Step 1: Determining What You Need.
First, you need to know what kind of footswitch your amp need. To do so, examine the back of the amp and find the footswitch input(s). Also, you need to know if each input(s) control only one or two functions of the amp (mono or stereo). On this amp, the left input controls the clean/gain channels switch and also the gain1/gain2 channels switch and the right one triggers the effect. Knowing this, we know that the left input need to be a stereo input and the right one only needs to be a mono input. If there's no inscription telling you which input controls which channel, you may need to look in the user manual, check online or open up the amp to check the type of inputs.
Knowing the type of inputs, we need to determine how the amp works and how the wiring will be. Plug your guitar in your amp and plug the right type of 1/4" jack cable (mono or stereo) in the footswitch input(s). With the cable plugged, play on your guitar and note which channels are active. Now, with a wire, touch the sleeve with one end of the wire and the tip of the jack cable with the other end of the wire (see pictures). Doing this, you're closing the circuit and your amp should react by switching a channel, note which one. Now, release the wire from the jack cable (opening the circuit), if the amp switch back to the previous channel, then you need a maintained (on/off) button. If your amp stays in the new selected channel, then you need a momentary button. A momentary button only closes the circuit while being pushed and opens it when released while a maintained button alternates between closing and opening the circuit each time you press it. Repeat this for the ring part of the jack cable (if stereo) and also for the other jack cable (if there's one). There's one picture where I show a neat little chart to easily note everything seen earlier, I filled it with the informations needed for my amp.
NOTES: If you found out you need momentary buttons, you may want to consider forgetting about LEDs or asking me for help on the subject. I could possibly update this Instructable to show you how to adapt the wiring for the LEDs to work with momentary buttons. It would add components also, make the wiring a bit more complicated and space consumming.
Step 2: Gathering Tools and Materials
- Soldering iron and solder
- Multimeter (optional but very usefull)
- Drill and drill bits
- Wire cutter/stripper
- Metal file
- Some crocodile clips (optional but very usefull)
- Measuring tape, a ruler or a caliper
- Container (with screws included) (I recommend a plastic hobby box)
- LEDs (different colors) [in my case, 1x red, 1x orange(which is more yellow than a yellow LED, duh!) and 1x blue]
- LED holders [in my case, 3x]
- Resistors [in my case, 3x]
- 1x Switch SPST 12V
- 1x 9V battery holder
- 1/4" jack female connector(s) [in my case, 1x stereo and 1x mono]
- DPDT metal footswitches [in my case, 3x maintained]
- Heat shrink tubing (optional)
- Rubber feets
- Spray paint (optional, for painting)
- Painter's tape (optional, for painting)
The hardware explained:
Container: Like i said, I recommend a plastic container because it's easy to work with and plastic don't conduct electricity. In my case, the dimension of the container are: 8.5" x 4.25" x 1.75".
Wires: Since the current loads involved in this project are rather small, I would recommend using some 20-22 gauge wire. Because I only had 18 gauge wire, I've used it for the "channel switching" circuit but for the LED circuit, I went to the store and bought some 22 gauge wire because soldering a LED on some 18 gauge wire and having to tuck it in tight spaces isn't the greatest thing in the world haha!
LEDs: I recommend using 5mm LEDs since 3mm LEDS look way too small next to the footswitches. In order to choose the right resistors, you need three informations, the voltage drop,the max current and the power rating. The voltage drop is the amount in Volts that is "lost" in the LED (usually a constant value for each color). The max current is the maximum current in Amps the LED can support. In general, the maximum current a LED can support in 20mA (milliamps or 1/1000 Amps). The power rating is the maximum power (in Watts) a resistor can dissipate in heat. For the voltage drop, refer to the place where you buy your LEDs, search on the internet or if you're using the same colors as me, use my values. In my case, the voltage drop for the red and orange LED was 2V and 3V for the blue one. Since I don't want to buy a different resistor for each LED, I'm gonna use the lowest value to find the right value for the resistors (2V in this case).
Resistors: For this project, the LEDs and the resistors are gonna be wired in parallel which means that every resistor has to "drop" the voltage from 9V to the value of the lowest voltage drop value we found earlier. Also, the maximum current we want in our LEDs is 20mA. With those information we're able to use the following equation: V = R * I where: V is the voltage (in Volts), R is the value of the resistor (in Ohms) and I is the current (in Amps). Since we want the resistor to "drop" the voltage from 9V to 2V, the difference of voltage seen by the resistor is 9V-2V=7V thus making the value of V equal to 7 Volts. With the values we get: 7 Volts = R * 0.02 Amps ----> R = 7/0.02 -----> R = 350 Ohms. Now, not every value of resistance is available on the market, the closest value to 350 for a resistor is 360 Ohms. For the power rating, the equation is P = R * I^2 where: P is the power (in Watts), R is the value of the resistor (in Ohms) and I is the current (in Amps). With the values we get: P = 360 Ohms * (0.02 Amps)^2 -----> P = 0.144 Watts, which means you need a resistor that can atleast dissipate 0.144 Watts, the nearest power rating is 1/4 Watts. With this being said, you need to buy one resistor for each LEDs you plan on using (which is the number of footswitches you need). The value of those resistors is 360 Ohms and 1/4 Watts. In my case, there was no 360 Ohms and 1/4 Watts resistor left so I bought 1/2 Watts resistors instead...
SPST switch: SPST stand for single pole, single throw. We need this switch to prevent the battery from always sending power to the LEDs because you don't want the LEDs to be lit when you don't use the footswitch.
DPDT footswitches: DPDT stand for double pole, double throw. I won't go in deep as why we need DPDT footswitches but to make it simple, we need the footswitches to operate the "channel switching" circuit while operating the "LED circuit". Depending on how your amp works, you may also need to close the "LED circuit" while opening the "channel switching" circuit. Needing to operate two circuit with one switch = double pole. Needing to close a circuit while opening the other = double throw.
Heat shrink tubing: Like i mentioned, this is optional. When I make electrical connection, I like to protect those with heat shrink tubing. If you don't want to use it, just don't.
Step 3: The Container
Before beginning the wiring, you need to drill holes in the container to fit all the hardware. You need to drill holes for the 1/4" jack input(s), the LED(s), the footswitche(s) and the battery switch. As your hardware may differ from mine, I'm not gonna give dimension for the holes. If you have a caliper, use it to find the diameter the hole needs to be. Always begin with a small hole and gradually make your way up to the right dimension or else you could break the plastic case. Use a metal file to smooth the edges.
Also, for the battery switch, I had to use a spade bit (shown in pic) in order to make a hole big enough because my drill bits kit stop at 1/2". To be honest, I wouldn't recommend anybody to attempt drilling the side of an hollow container with a spade bit. It can be dangerous and you can end up injuring yourself. With proper clamping and support, I've managed to secure the workpiece enough for me to decide I wanted to try it out. Once again, I don't recommend doing so and the best option is to either find a drill bit big enough or a smaller switch...
Also, I used a 9v battery adapter without any casing to support the battery so I made one using a piece of plastic and some hot glue. I also glued some rubber feets on the back cover of the container in order to prevent the battery for moving back and forth. If you have a container big enough to accommodate a 9v battery holder, I would recommend you get one or do the same as me.
Step 4: Painting
With the container drilled and ready, it's a good idea to paint it now because if you wait after the wiring is done, you'll have to take it apart to paint it. Since I'm a big fan of Rammstein and I find the cover of their album named "Reise Reise" really nice, I reproduced this orange and white pattern on my footswitch. I'm using normal spray paint. Just make sure your paint will bond to the type of surface you're using and that the surface is clean before applying paint.
I'm not a pro when it comes to painting something so I'm gonna refer you to this Instructable: How to properly apply spraypaint.
Although, I'm still gonna explain you what I did to paint my container.
First, I sanded it with a 180 grit sandpaper until the surface was mate and rough to the touch. I sprayed 4 coats of white paint. I taped the pattern. I sprayed one more coat of white to further enhance the seal with the tape (Thanks to the linked Instructable for this tip). I sprayed 3 coats of the orange color. Removed the tape 1 hour after the last coat. Then, I let it dry for a day before doing some touch-ups. Finally, I sprayed 3 coats of clear.
Step 5: Wiring
NOTES: If you're not sure how your components are working, take a multimeter, set it to the continuity mode and find which pin is which.
At the bottom of the schematic, you got the 9v battery holder. S1 is the 12v SPST switch for the battery. DPDT1, DPDT2 and DPDT3 are the footswitches. R1, R2 and R3 are the resistances. You got the LEDs with their color written over it. Both 1/4 jack inputs are in the top of the schematic.
For the battery switch (S1), you should have 2 or 3 pins on it, the third pin (usually a gold pin) is to light the LED contained in the switch but we don't need this function. I found a neat little drawing to show you where each pins of a DPDT switch are located on the schematic. Also, if you happen to have a 1/4 jack mono input with more than 2 pins or a stereo one with more than 3 pins, you got an input with an integrated switch that can be used to determine if there's a cable plugged in it. Once again, to determine which pins is which, use a multimeter set on the continuity mode and touch the mystery pin with another part of the input (in example, touching one pin and the tip part of the input).The reason why I choosed the little 12v SPST switch over using 1/4 inputs with an integrated switch is because I want my footswitch to work with as much different amplifier as possible. So if one day I need to only plug one cable, I don't want the footswitch to be waiting for the other cable to be turned on.With this being said, it could be done with the jack inputs integrated switch but the wiring would be more complicated than just throwing a simple switch in the circuit... Also, for some reason, you could want to turn off the LEDs while still using the footswitch.
For the LEDs, you should to refer to the chart I made in the "Determining what you need" part in order to visualize this. As an example, if you want the LED for the clean/gain channel to be lit when gain is selected, you will need to open the channel switching circuit when closing the LEDs circuit. To do so, I wired my channel switching circuit on the #5 and #4 pins of the footswitch and the LEDs circuit on the #2 and #3 pins (referring to pictures) so that whenever the circuit is closed for the LEDs, it's open for the channel switching. On the right footswitch the wiring is inverted just to make the wiring easier but the logic remains the same.
NOTES: While wiring my footswitch, I've used some crimp connectors to be able to change the way the LEDs react to the switch being closed or open if one day I need to use this footswitch on another amp that work differently. If you don't care, don't bother with that and solder the wire to the pins directly.
It's always a good idea to use crocodile clips to connects the components (as a test) instead of soldering everything in place without being sure everything is working fine. Also a good idea to solder the channel switching circuit and testing it before moving on to the LEDs circuits.
If even after this you still got question about your components and how to use them, search on the internet or just ask me your question and I will try to answer it as quickly as possible.
Step 6: Finishing
You're almost done! Now it's time to add the rubber feets to prevent the footswitch from wandering around, add a 9V battery and close the container with screws.
After all those hours of work, your footswitch is now finished. Congrats! Now have fun using it and be proud of yourself !
If you have questions about this project, leave a comment below!
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