Blind-Summit
THE GUITAR PLAYERS COMMUNITY

Make Your Own Overdrive Stomp Box

This effects unit was inspired and a slightly modified version of "Joe’s Easy Drive" by Joe Davisson from the Guitar Effects Projects website. I added a DPTP stomp switch into the schematic to allow you to turn the unit on and off (overdrive / bypass).

I have also included some Maplin Electronics codes for ordering the parts since this can sometimes be a slight issue. If you live outside the UK, the parts should still be easy to find if you have a RadioShack or similar store. I have built my unit into a transparent blue acrylic box. Maplin Electronics has this down as an iMac feel box or something along those lines. I decided to give it a try as the standard white acrylic and the aluminium boxes looked a little dull. If you decide to use a metal "project" box, please ensure that you opt for the plastic 1/4" jack plugs otherwise you will short out the connections.

As with most electronic projects of this sort, you should have some basic soldering skills before you attempt this. The use of a multimeter is nice for checking connections, although it is not essential.

Parts Needed

• Thin gauge multi core wire (not solid core - this is too stiff to fit easily into the project box)
• 1 x Project Box
• 1 x 9v Battery
• 1 x Battery Clip
• 1 x Stereo 1/4" Jack
• 1 x Mono 1/4" Jack
• 1 x 680Ω Resistor
• 1 x 68kΩ Resistor
• 2 x 220kΩ Resistor
• 2 x 1N4001 Diode
• 1 x 22μF Capacitor (polarised electrolytic type)
• 3 x 0.1μF Capacitor (un-polarised ceramic type - usually labelled "104")
• 1 x 0.01μF Capacitor (un-polarised ceramic type - usually labelled "103")
• 1 x 0.001μF Capacitor (un-polarised ceramic type - usually labelled "102")
• 1 x 2N3904 Transistor

As well as this, you will also need either some veroboard or to get yourself a PCB kit. For this project, I tried out making my own PCB for the first time and had good results. It’s often a lot easier that veroboard as you don’t have to remove parts of the track, but it is more time consuming and more expensive. I have included the PCB layout but it’s up to you!

Tools Needed

• Soldering Iron & Solder
• Pliers & Wire Clippers
• PCB Etch kit, copper backed board (for PCB version)
• Veroboard & Track cutter (for veroboard version)
• Screwdriver (to fit project box screws)
• Drill & Bits (to cut holes in project box for 1/4" jacks and holes in PCB)
• Assorted Files (to clean up edges of cut holes or PCB / Veroboard)
• 3rd Hand / Jig / Clamp (to hold components / board for soldering)

Once you have all the parts and components, you will need to decide on the veroboard or PCB method. With the PCB method, you will firstly need to draw out the schematic onto the copper coated board. I bought a beginners PCB kit from Maplin Electronics that had the boards and etch material included. They recommend using a Edding 3000 or Edding 400 touch up pen, or a nitrocellulose based pen. Adhesive symbols can also be used and give a neat finish. I had none of the above so I used a fine tipped permanent marker pen - the type used for writing on CDs or overhead projector transparencies. The results were a little rough, but it worked ok.

Here is the circuit diagram in PBC format showing the location of each component:

Here is the PCB to print out / trace etc.

Printed Circuit Boards (PCB’s) can be created in several different ways. The basic principal is to draw or cover over the outline of the circuit diagram (as above) onto a copper covered board. The board is then processed to remove all but the outlined marks by means of "etching". After the board is washed and cleaned, a copper track remains in the form of the initial diagram. You can buy boards that use a solution of sodium persulphate or similar to chemically etch the copper away, and some boards are coated with a light sensitive material that allows light to be used to etch. Whichever way you choose, you will need to make sure that the design is about 4×5cm in size. The tracks should be 1.5 ~ 2mm wide, and the circles that define where holes will be cut to place the components should be 3~4mm in diameter. If the track is too thin it can break off easily and the heat from a soldering iron can cause it to lift from the board. If the track is too thick you may accidentally solder across 2 lines creating a short, and it can also look a little untidy.

If you print out the diagrams to copy, just make sure they are the right size. If you draw onto the copper board with a marker pen, be sure to leave a well drawn diagram with a good covering of ink for the lines.

After the diagram is drawn, you can then cut out the section of board. If you cut a piece out first before designing the tracks, you risk mistakes and having to squeeze things in, so the advice is draw out, then cut!

You can now etch the PCB with whichever tools you have chosen. My kit came with 100g of sodium persulphate to be mixed with 0.5 litres of hot water (50 - 60°C) but this was to develop all of the copper boards. For this small piece, I used two teaspoons full into about 150 or 200ml of water - mostly from a boiled kettle with a little cold water to get the right temperature.

Clean and wash the board thoroughly with cold water. Dry.

After the etching is complete, you will need to drill out the holes for the component legs to slot into. I used about a 1mm diameter drill bit, being careful not to remove the entire copper circle from the board. If you do make any mistakes, there are touch up materials that can repair bust track. You can get thin strips of copper tape to repair track and pens with a conductive "ink". Ideally you should avoid making mistakes by just taking your time, but all is not lost!

Once all of the holes are drilled, you can start to solder in the components. Remember that the diagram shows the copper track that will be on the underside of the board. The components should be slotted in from the plain side so that the metal legs protrude out to the copper side for soldering. I apologise if this is sounding like an "idiots guide" but too much detail is not always a bad thing as I have seen people solder the parts on the wrong side before! I won’t however, go into details on how to solder correctly.

Start with the resistors - bend the legs at 90° forming a sort of |_| shape and slot them in so that they lie flat against the board. This lets you keep the board neat and ensures that components won’t get broken off. Solder the two diodes and the μF capacitor (ensuring that you get the polarity correct) in the same way. Next solder in the 5 ceramic capacitors - these are un-polarised meaning that they can be slotted in either way around just like a resistor. Lastly the transistor needs to be soldered. This is a relatively delicate component and is damaged by heat. I managed to solder it in place quickly without damage since I am pretty handy with a soldering iron, however you can hold each leg with a pair of pliers and use this as a heatsink. You may also use a clamp or just get a friend to help as you can quickly run out of hands! Check carefully the transistor pins as these are vital to the circuit working. The diagram above shows a top down view on the transistor. With the legs downwards and the flat edge to the left - the top pin (furthest from you) is the Emitter (E) the middle pin is the Base (B) and the bottom pin (closest to you) is the Collector (C).

Next job is to solder in the battery clip and the wires connecting up the DPDT (double pole, double throw) foot switch. Cut about 5cm or wire for the switch - you need enough to allow you to remove the lid to replace the 9v battery, but not so long that it becomes difficult to close the lid with wire slipping out. Leave about the same for the wires to the two jacks.

If you have not noticed or are still wondering why we use a stereo input jack, even though a guitar uses mono wires - this is to turn on and off the unit. When the guitar lead is inserted, it connects the stereo jack’s sleeve and ring terminal and completes the power to the circuit. This saves you from having a power switch or having to put the battery in and out each time you use the unit.

The jacks I used from Maplin Electronics needed a 10mm hole cut. The DPTD switch needed about 12mm)

After you have finished soldering, plug in the 9v battery, and plug in you guitar and amp to the clean channel. The footswitch will let you switch from overdriven (using the effects box) to bypassed (ignoring the circuit and going directly to your amp).

It is fairly common to make a simple mistake when building any circuit. This is a fairly easy one to start with, but you can still get the transistor pins wrong / the 22μF capacitor the wrong way around etc. This is why I mentioned a multimeter earlier. It will let you follow the circuit around and work out mistakes. I have devised a really short problem solving list:

1. If the unit does not produce any output - i.e. you get no sound, then you have either:
a) wired the transistor in wrongly
b) damaged the transistor, probably with heat
c) broken track

2. The amp makes a buzzing sound when you touch the battery or the metal parts of the guitar: The jacks are probably wired in wrongly

3. The switch does not work correctly: Check that the tips from the jacks switch from a connection to each other and to the board. This is the part that allows you to bypass the unit direct to your amp.

I decided to also use a hot melt glue gun to fix the PCB to the inside of the project box. Just a small blob helps to keep the board in place so that the battery fits in easily, and the lid closes properly. I’m sure there are neater ways to do this using screws and fixings but I just wanted a "quick fix".

If you get stuck with this and the basic Q&A doesn’t help, either visit the workshop section of the forum or drop me an e-mail at webmaster@blind-summit.co.uk. I will try and add the veroboard diagram in the future but until then, you should be able to figure out the layout from this schematic:

Just take your time and follow the path from the +ve terminal of the battery and make sure nothing shorts. The sets of 3 horizontal lines like those right at the bottom mean that these all form the -ve rail and effectively should all join together. If it doesn’t makes sense - compare it to the other diagrams at the top of the article.

NOTES: After building and using the pedal for some time, I wanted to add some pointers. I found that it gives a very heavy bass response at the sacrifice of some top end treble. My electronics ability is too limited to work out just yet, what components need to be modified. If you happen to test out a different resistor / capacitor configuration that gives better results, then let us know about it on the forum, or as a comment to this post.