Mod.It.Yourself (M.I.Y) Part 3 – Switches
The following is a guest post by Christian Moraga (@cubisteffects). If you are interested in guest posting, please contact me!
Welcome to Part 3 of the Mod.It.Yourself series where we have previously looked at the basics of Tools and Techniques in Part 1 and how to mod the Diode Clipping in a pedal in Part 2. Part 3: Switches will look at an important component in the pedal modder’s toolkit. Switches are mechanical devices that allow an instantaneous flip to either turn part of a circuit on or off (break the circuit), or introduce a new part to the circuit. The latter function is useful in doing reversible modifications, or mods that use the original stock component. This part of The M.I.Y series will explain a bit about common switches and some ideas on how to use them in your own pedal mods.
The two most common mechanical switches used in modifying pedals are the push button switch and toggle switch.
Both of these switches use common nomenclature for their components that must be understood before selecting them for your next project. Below is a look at some of the more common names of switches that are used for pedal mods and an explanation of their specs.
Each switch is named with respect to the functions of their contacts, i.e. the part of the switch that is in contact with your wire, component, PCB etc. Also called a lug or pin. The two terms are poles (denoted by P) and throw (denoted by T). A pole is the number of switch contact sets of pins/lugs, and is labelled SP- for single pole, DP- double pole, 3P- for triple pole etc. The diagram below shows the poles of a 4PDT switch.
Most switches used in pedals have three pins per pole. The center pin is common i.e. is always connected to either outer pin of the three. Moving the toggle either up or down selects (as shown in the photo below) between these two connections or conducting positions. These positions are known as throws and are denoted -ST for single throw or -DT for double throw. A single throw switch only has two pins with the third pin shorting to ground, thus having only one position.
Common switches used in modifications are single pole double throw (SPDT) or double pole double throw toggle (DPDT) switches, and true bypass foot switches are known as triple pole double throw (3PDT). Using this knowledge of switches, here are a couple of mods you can try on your next pedal designs or mods.
KILL SWITCH
To get a stuttering effect made famous by guitarists Tom Morello and Buckethead in stompbox form, you can make use of a type of push button switch called a momentary switch. By using a push-to-make momentary or “normally open”, when pressing the switch you are breaking the circuit thus creating a staccato effect. To do this, all you need to do is cut the wire that goes from the output of the PCB to the bypass switch. Wire each of these two ends to a normally open SPST momentary switch and you have a momentary kill switch. The effect signal will stay on until you step on the switch, cutting all volume of your signal. By pressing at rhythmic intervals, you can create unique guitar rhythms heard in many RATM riffs. Momentary switches are great for these “stab” like effects and can be used for feedback loops, or wiring to a potentiometer in a delay pedal to get that spaceship, oscillation sound.
DIODE CLIPPING SWITCH
As previously discussed in Part 2 of the M.I.Y series, we can mod a pedals’ clipping diodes to create a different tone of the distorted sound. We could use different diode material, symmetry, combinations etc to get our desired sound. But what if you liked two diode sounds and wanted to switch between them? Using an SPDT switch, you can do just that and is a common feature on many effects pedals.
The schematic below [PIC 5] shows the clipping diode structure of many distortion pedals – a hard clipping pair at the output of the IC.
One end of the pair shunts to ground, while the other end is in the signal path. If this end on the signal path (A) is wired to the common pin of the SPDT switch, we can then switch between two differing pairs of diodes. Wire the end of two pairs to ground, and the other end to (B) and (C) of the switch and you can select between your favourite clipping tones. The symmetry of the clipping can be controlled using this switching layout as well – just use different symmetrical pairs for (B) and (C).
You can also use this principle to switch between two components of differing values i.e. the output capacitor to provide more/less bass in the circuit. Remove the initial capacitor from the PCB where one pad will have one wire running to (A) and two wires from the other pad to one end of either capacitor you wish to switch between [PIC 7].
Hopefully this information and diagrams will give you ideas on how to mod your next pedal, or to modify your next pedal build. Also, I would suggest getting a multimeter with a continuity test function. By putting either probe on any two connections, a beep or sound should be heard. This is very useful to test your new connections.
Happy modding,
C.
About the author.
Christian Moraga is the owner of CubistEffects.com located in Sydney, Australia. Christian repairs and mods most brands of pedals like BOSS, Ibanez, EHX , Arion, MXR, Danelectro, Marshall, Dunlop, VooDoo Labs, Digitech, DOD etc and specialise in Big Muffs and ProCo Rats. He also makes custom switching and loopers for your pedalboard needs. A/B, True Bypass, Tap Tempo etc.
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