A Guide To Capacitors For Guitar Pedal Building
WHAT IS A CAPACITOR?
Capacitors are two-terminal passive electrical components that are up there with resistors to be one of the most used components in circuit design. They contain two conductive plates which could either be metal, foil or discs (depending on the type of capacitor) with a nonconductive dielectric material (e.g. ceramic, glass, plastic, air or paper) that helps increase the charge of the capacitor.
The main purpose of a capacitor is to store energy, just like a standard battery does, but we can also use capacitors for filtering signal and shaping the tone of your guitar.
WHAT TYPES OF CAPACITORS ARE THERE?
While capacitors come in all shapes and sizes, they will all contain at least two electrical conductors (known as places plates) separated by a dielectric (like an insulator) and follow one of two formats. Radial or Axial.
Axial capacitors are components that have connecting wires on each end capacitor and are generally found in point to point hand-wired & turret/eyelet board circuits.
Radial capacitors resemble cans with both connection wires coming from the bottom and are much more common when building DIY guitar pedals as they require much less space on the board.
Electrolytic capacitors are generally large value capacitors and measured in microfarads (uF). Unlike every other capacitor we use, these are polarised and it’s crucial to ensure you take note of this when adding them to your project.
The polarity of the capacitor should always be visible down one side of the component. We’ll normally see that the negative side of the capacitor is highlighted with the other side being positive.
POLYESTER, BOX & METAL FILM CAPACITORS
Polyester, Box & Metal Film capacitors are your middle-value capacitors and will be measured in nanofarads (nF).
These will be the most common capacitors you’ll be using when building guitar effects pedals and will help you control all the filtering and tone shaping of your pedals.
They come in lots of shapes and sizes but the easiest way to identify them is through the process of elimination. If it looks like a can, it’s an electrolytic capacity. If it’s circular, it’s a ceramic capacitor. Anything else will more than likely be a polyester, box or metal film capacitor.
These are our smallest value capacitors and are measured in picofarads (pF). Ceramic capacitors are great for working with high frequencies but can sometimes create microphonic issues. We’ll generally stick to polyester, box or metal film capacitors as they’re much more reliable and can cover many of the same capacitance values.
HOW ARE CAPACITORS MEASURED?
Capacitors are measured in units called Farads (F) and are generally found in Picofarad (pF) which is a trillionth of a Farad, Nanofarad (nF) which is a billionth of a Farad, and Microfarad (uF) which is a millionth of a Farad.
As previously mentioned, capacitor values can be estimated through the type of capacitor it is.
- Electrolytic capacitors are larger values and almost always measured in Microfarads (uF).
- Poly, Box & Metal Film capacitors are medium values and are generally measured in Nanofarads (nF).
- Ceramic capacitors are the smallest values and cover Picofarads (pF) through to the lower Nanofarad (nF) values.
HOW TO TEST A CAPACITOR?
The best way to accurately test what the value of a capacitor is is with a digital multimeter. However, the text found on the capacitor can help you identify what the values are.
Electrolytic capacitors will always contain the uF value along with a voltage rating down the side. Usually on the other side of the polarity markings.
For poly, box, metal film & ceramic capacitors, you can take a look at the code to get an indication of the value. For example, if your ceramic capacitor contains the code ‘101’, the value of that capacitor is 100pF.
I’ve created a tool below to help decipher what these codes mean. Simply type in the the number on your capacitor to find out what value it is.Enter Code Here Check
If my capacitor code tool isn’t able to help you identify the value of your capacitor, you’ll need to get your digital multimeter out.
Unfortunately, not all multimeters are created equally and not all multimeters have the ability to measure capacitance. However, if yours does, it will have a pF, nF or uF setting.
As previously mentioned, you can estimate the capacitance value of a capacitor by the shape of it. If it’s an electrolytic capacitor that you’re looking to measure, set the meter to uF as this will most like measure in the microfarad range. If it’s a poly, box of metal film capacitor, initially set your multimeter to nF as it will most likely be in the nanofarad range. Finally, if your wanting the value of a ceramic capacitor, set your multimeter to pF as it will most likely register on the picofarad range.
If the multimeter shows a figure to lots of decimal places, take it down a rating (e.g. uF to nF). However, if your multimeter is showing a very high capacitance with a lot of zero’s, increase the rating (e.g. pF to nF).
HOW TO SAFELY DISCHARGE A CAPACITOR?
Thankfully, when it comes to creating DIY guitar pedals, we’re not dealing with large voltages so there is very little risk in seriously hurting yourself. However, it’s always better to be safer than sorry, to fully understand the components your working with and how to use them safely.
As capacitors store electrical energy, there is the chance that they will still have some charge once you disconnect them from a power source. While this will dissipate over time, the safest way to handle them is to manually discharge them.
To safely discharge a capacitor from your guitar pedal, you can take a 2 Watt 10K resistor and use it to bridge both wires coming from that capacitor. This will allow the charge to run down much quicker making it safe to work with the circuit. This is also known as a bleed resistor.
Be careful not to touch the charged capacitor with your bare skin as this could be fatal and always use safety gloves where possible.
That’s my guide to capacitors for guitar pedals, one of the most common guitar pedal components.
Why not check out my other posts about the other common components when building DIY guitar effects pedals here:
If you’re new to this and would like to know where to buy capacitors for your DIY effects pedal projects, check out my guide here: