Feeling bored in the evenings?.. enjoy burning your hair on a hot soldering iron?… do you play the guitar?…
So I was sitting there one day strumming away some power chords when I suddenly had a thought… “It’d be really cool if I had a distortion pedal…”. So I vaguely started looking round in shops at the pedals and realised that they’re fairly pricey things. Suddenly with a flash of inspiration I remembered seeing the circuit diagram for a simple wah-wah in an electronics book when I was doing my GCSE, so armed with that knowledge (and my GSCE electronics experience) I decided to find a circuit diagram online and construct my own. If you’re planning to do this then I strongly recommend the sites listed on this page, this writeup is my own advice and the considerations you should think about when constructing your pedal.
I guess most of you will want to know if it’s cheaper to build your own pedal than buy on in the shop. Well, yes and no. Yes I guess it’ll cost less money in parts, but no you won’t get the same sort of quality as a store-brought one unless you’re a professional with your own etching kit and high audio standard components… in which case why are you reading this?
A quick internet search will furnish you with a circuit diagram, or if you can’t be bothered then just follow some of the links on this writeup and they’ll point you in the right direction. As well as original designs you can also find diagrams for vintage pedals which are no longer in production. I suggest that initially you try and find a fairly simple design with only a few active components.
Equipment and tools
Soldering Iron – This doesn’t have to be a top of the range one, I managed to pick one up for £5. Most will come with a fine point tip as standard. You may want to consider buying a ‘chisel’ tip as it can make it a little easier to heat the correct area and insert the solder, I’ll mention this in a little more detail later.
Small side-cutters – The small spring-loaded type are best. Anything too big will just get in the way when you’re trying to tidy up ends.
Pliers (Long nose) – Again the small spring-loaded types are really useful. They can often be bought in a pack with some side cutters at many chain-DIY stores.
Modelling knife – These are always useful, but chances are you’ll have one lying around somewhere.
Heat sink – You can buy small clip like devices which help dissipate some of the heat from soldering to avoid damaging components. You could use a par of pliers, of wrap some copper wire around the leg but for ease of use and the small cost, investing in one of these is well worth it in my opinion.
I’m not going to go into exactly how each component works, but I’ll give a brief overview of the types of component you’ll probably be using and roughly what they do.
Resistor – Does exactly what it sounds like. They provide a resistance for current and will frequently be used to create a voltage drop. The most common type is ‘Metal Film’. They are small, vaguely cylindrical things with a leg coming out each end. They don’t have polarity so you can put then in either way round. The stripes on them indicate the value of the resistance (There is a good description in the Resistor node). Remember that you can sum resistors in series to get specific values.
Base unit: Ohm (500Ω; = 500R or 0.5K)
Capacitors – They store small amounts of charge and are used in many aspects of electronics, although the most traditional use is timing. Common types:
- Ceramic – Small orange discs with two legs, they are not polarised
- Polyester – Bigger rectangular components with two legs, again they are not polarised
- Electrolytic- Cylindrical components, these are polarised and must be connected in the correct way. It is usually the negative leg that is marked on the capacitor. These come in both radial and axial forms although there is no real difference apart from the way they will sit on your board
(Usually measured in pF, nF, μF)
– Also called a pot
or a variable resistor
, they are used for volume
etc. controls. A potentiometer is basically a resistor which has a slider allowing any point of resistance to be taken by the middle pin
. When connected between two points of different voltages it acts as a potential divider
allowing any voltage between the two values to be ‘selected’. As well as there being different values of resistance, they are also available in linear
types. If you are not sure which to use then a general rule is to use a linear unless it’s a volume
control (As sound level works on a logarithmic scale) in which case use logarithmic.
– Essentially they allow current to flow in one direction and not the other. The stripe
on the component shows which end the current will flow from. They can be made from two different materials (silicon
(Si) and germanium
(Ge)) and it should be specified which one to use on the circuit diagram although germanium diodes are not common so you may have to use a silicon instead.
SPDT and DPDT switches
– Stands for ‘Single Pole Double Throw
’ and ‘Double Pole Double Throw
’ respectively. The easiest way to explain them is to think of a SPDT switch as a set of railway points
. The signal from the common pin can be switched between the two pins just like a train can be directed to two different routes from a set of points. A DPDT is just two SPDT switches controlled by the same mechanical
switch. You will probably want to find a special heavy duty toe switch
– They could be described as electronic switches, however in an effects pedal
they are more likely being used for their amplifying
properties. Transistors have three legs, the Collector, the Base and the Emitter.
(IC’s or ‘chips’
) – For example Op-amps
, 555 timer
s etc. You might want to check the data sheet
for your IC to confirm the pin outs
. Remember that you should not solder these directly to your boards as you will probably damage the component. Instead buy a DIL
(Dual In Line) socket with the same number of pins as your IC and solder that to the board. Then when you come to test the circuit, all you have to do is push the IC into the DIL socket… and when you try and take the IC out of the DIL socket I guarantee that you will stab your thumb with the pins and bend the legs…
The pins for an IC are numbered as shown below (I’ve shown an 8 pin, but the system is the same for any number of pins). Notice that the numbering is relative to the notch
on the top surface of the IC.
Warning: IC’s can be sensitive to static, so earth yourself before touching them.
| U |
Wire – Any standard electronics wire will do (22 gauge and smaller – the number gets bigger as the wire gets smaller).
Battery clip – Most pedals ill be 9V so you’ll want a clip for a standard PP3 (small rectangular) battery.
Stripboard – Unless you want to try and soldier all your components together in mid-air, or you have your own etching kit then you’ll need some stripboard. This is plastic board with copper strips on one side, holes drilled through and it looks roughly like this:
|O O O O O| |O O O O O| - Copper
|---------| |---------|_ No copper
|O O O O O| |O O O O O|
|O O O O O| |O O O O O|
The rows are linked by copper so any connection
you solder on one row will be connected electrically to anything else on that row of copper. The break in middle of the board is to allow IC’s to be positioned across it (If it wasn’t there then the right and left legs of the IC would be connected).
1/4" Jack Sockets
– It’s best to buy stereo
sockets even though guitar plugs are mono
. The socket has three connections: Tip
. The signal
will only be passed across the tip and collar connections, however the ring is generally used to complete the circuit and act as an ‘ON switch
’ when the input is plugged in.
– The standard black insulation tape
will always be useful.
A breadboard is basically the same a stripboard. The rows are connected and the columns aren’t. The difference is that a breadboard allows you to just poke wires and component legs in the connection holes to test and develop the circuit without committing to your soldered final product. Breadboarding is an important tool if you are developing your own design however it is slightly excessive when just following a circuit diagram.
Remember that eventually your circuit board is going to have to be put in a case of some sort so be mindful of how big it is. This does not mean that you should positioning all components as close together as physically possible because you will end up making a mistake. It is a good idea to get a fine nib pen of some sort and plan out roughly where things are going to be on the ‘non-copper’ side of the stripboard. Solder sufficient lengths of wire to the connections on the external components (Switches, pots, Jack sockets etc.) so that they reach where they will eventually be mounted. It is generally expected that connections to these sort of components should be enclosed in heat shrink, but a little black insulation tape once you’ve finished will do the job. If there are some points where you have to have a wire link across the board, make sure that it sits fairly close as huge loops of wire just get in the way when soldering other components.
Soldering – Rough guide
I’m not an expert at soldering, but it is important to know what is a good connection. All the components should sit on the NON-COPPER side of the board with the legs poking through and soldered to the copper on the other side.
Push the leg of your component (or wire) through the board in the correct hole and bend it over slightly so the component sits fairly low (although its best not to have the component touching the board) on the other side. At this point you might want to trim a little off the length of the legs just to make them easier to use.
Heat sinking is important and you will need to heat sink when soldering for most components, I advise that you heat sink all your components just to be sure. This is done by attaching something metal to the leg between the component and the board. You can use a store bought heat sink, a pair of pliers or even by wrapping some copper wire around the leg.
Make sure your soldering iron is nice and hot, then position the tip touching both points of the connection to heat up the metal. Push the end of the solder onto the tip of the iron until a small amount has melted. If you are really lucky then it will ‘flow’ between the leg and the copper of the board. Most likely however it will stay as a small blob so you need to continue to heat the metal and keep the solder in the correct position until is ‘flows’ onto the leg and the board. A good connection looks like a smooth curve between the leg and the board. Any connection that is bulging outward has not flow onto either the leg or the board correctly.
Do not mess about with it for too long, if you are having trouble with a connection the remove the iron, let it cool and try again. Heating the board for too long can cause the copper on the board to separate from the plastic. Once the connection is complete, leave to cool for a few seconds and remove the heat sink and trim the excess part of the leg (or wire) using the side cutters. If you are having trouble getting a good ‘flow’ then try cleaning up the copper with some wire wool.
I advise you do a few trial connections if you are unsure about the process.
Soldering irons are hot! – do not touch the metal part, do not leave the room with them switched on or hot, do not let it come into contact with anything which isn’t supposed to be soldered... doing any of things things could result in much non-goodness!
Always use lead-free solder!
Solder in a well ventilated place!
Most solder contains flux which is not good for you if you inhale the fumes, and can also spit when heated so try not to get it in your eyes!
What if it doesn’t work?
DON’T PANIC! … It could be something very simple. Before ripping out all your components and starting again, do the following things:
- Check everything is inserted, like IC’s in DIL sockets and the battery (surprising how often people forget this)
- Check no connections are loose
- Look at your soldering, are there any points where the solder might be touching the copper track next to the one it is on?… if so use a fine blade to clear the gap.
- Check that component legs aren’t touching each other.
- Go through your circuit diagram checking that what you’ve put on the board is the same as what it says on paper.
If this doesn’t work, and you’re fairly sure you’ve connected everything together correctly then it might be you’ve heat damaged
one of your components. This is most likely an active component
like a transistor.
Once you are happy with your circuit then you will want to case it in something because stepping on the circuit board won’t do it much good. Most electronics suppliers sell enclosures and you can pick up a plain metal box fairly cheap assuming you don’t have the equipment to build your own. At this point you either need to have a drill, or talk nicely to someone with a drill so you can put holes in your case to mount the external components. The manufacturer should give details of how big the hole needs to be, but if they don’t then you should be able to measure it. Switches, pots and sockets will generally come with a nut on the threaded part of the shaft. Simply take that off, poke the component though the hole and put the nut back on to secure it in place. You must also insulate your components (especially jack connections) from the case, you can get plastic inserts however insulation tape around the inside of the hole will do the job.
It is also a good idea to mount the circuit board inside the case to stop it getting thrown about when you accidentally kick it. I’ve used sticky pads (because I’m lazy) but if your are going to bolt it in remember to drill through an empty section of the board and use plastic spacers to raise it off the floor of the case slightly.
… and I guess that’s all I have to say!….. Good luck!
http://diystompboxes.com/pedals/ - This site has an excellent FAQ!
www.maplin.co.uk – UK component supplier
(If any of you people from across that ol’ sea know a good US supplier then I’d be happy to list it here)