This was inspired by http://www.instructables.com/id/Simple-overdrive-effect-pedal/, however I could not get it to work right so I did some research and made my own. The similarities are there because I made this (mostly) from parts I had purchased for his project.
Feel free to make your own improved version and post the instructable, but it would be great if you could put a link back here somewhere in the 'ible. Thanks!
Stay tuned for a video of my playing it.
Step 1: When to Use Distortion
There is nothing I hate more when a beginner, or even advanced guitarist steps out with the distortion cranked all the way up and starts playing chords. But you may like that. If you do, ignore my opinions.
If you have no idea what distortion is, start out by listing to a few songs.
Compare the song Jimmy Olsen's Blues by the Spin Doctors to Master of Puppets by Metallica. As you can probably hear, Jimmy Olsen's Blues has a very clean, well, bluesy sound, while Master of puppets has a rough, cutting sound. If you are still have trouble, listen to the song Around the World by the Red Hot Chili Peppers. That intro is a highly distorted bass, played by the master Flea. If you want, compare that to Blues For Mingus by Stanley Clarke. That is clean bass.
Now that you know what distortion sounds like, you should learn when to use it and how much to use.
In my own opinion, even if you are playing metal, never turn the distortion up so high that you can barely hear the chords you are playing. There is another no-no. High distortion with chords-too loud. In my opinion it sounds great with individual notes, but not with chords. But feel free to do whatever you like.
If you play jazz, your band-mates might not like the idea of you playing screaming distorted riffs, so go light on the distortion for jazz. Blues is the same way, but if you put a little bit of "tube scream" it sounds great. But as I said before, do whatever you like.
For all you bass players like me, distortion is even more fun! I personally like a medium amount of distortion, which this design makes. If you like more or less, by the end of the instructable, you will know how to alter it to your liking.
And lastly, other than the "rough" scream of distortion, what else will you notice?
First of all, distortion has some MEAN sustain... the notes keep ringing and ringing until you mute them. The other large thing is, HARMONICS. You can play harmonics with distortion incredibly easily, and they are as loud as the note. They have many different harmonics in them too. Great sound if you like harmonics like I do.
Step 2: What is Distortion?
So, now that you know what distortion sounds like, what is it?
Distortion is the clipping of sound waves, or AC at whatever frequency the note you are playing is.
The term "clipping" refers to the tips of each wave "clipped" off. There are several ways to go about doing this, but I went with the good ol' diode clipping method.
A diode looks like a resistor, but is not very similar. It lets a certain amount of voltage (called forward voltage drop) go past it, while the rest is sent to ground. For example, if you had a hose, imagine a valve that only lets 1 psi go by, while the rest is diverted to a different hose. Back to resistors; that resistor would have a forward voltage drop of 1. My design calls for a red LED, which has a forward voltage drop of ~2 and two 1n914 diodes with a forward voltage drop of ~.7 each (more like .65-.68). They are set up in such a way to let 1.2 -V and 2 +V through. That means if your signal was at 4 volts, you would be clipping 2.8 volts off of the -V and 2 off of the +V. That is without resistors and capacitors. See the simulated picture below for an example.
As you can see in the next picture, there is both soft and hard clipping. They will both distort the sound, but hard clipping is more metallic (think heavy metal music) while soft clipping sounds more like a tube amp turned up too high. They term soft and hard refer to the sharpness of the clipping. Soft is more curved, while hard has much more of an angle. See the image for a visual.
Step 3: What You Need
-Two 9-Volt batteries
-Four 100 ohm resistors
-One LM741 op amp
-One 1K ohm resistor (1000 ohm)
-One .1 uF capacitor (any type)
-Two 4.7K ohm resistors (4700 ohm)
-Two 1N914 switching diodes
-One red LED
-A project case
-Two mono 1/4" (6.3mm) female jacks
-One DPDT switch (two way 6 pin)
-One on/off switch
-Perf board (with copper rings on bottom)
-Two 9 volt battery holders (just take the tops off of two dead 9 volt batteries, the batteries will fit into them perfectly)
I also suggest getting a solder sucker and some soldering braid. Very useful stuff!
All of the above can be purchased at Radio Shack, so no need to hunt around. The total price should be around $10, unless you need a soldering iron. Those usually run about $10-$20.
Step 4: The Schematics
If you don't know how to read schematics, don't worry! Just pay attention to the notes on the images. You would be better off looking up how to read schematics, though, just to be safe.
Pay attention to the back of the LM741 package for the terminal numbers, if you get those wrong you could cook the amp. All the numbers on the schematic are right, just placement is funny, because the amp is a rectangle, while the schematic amp is a triangle. Don't ask my why... I didn't invent schematics.
When grounding, solder a stripped wire across most of the perf board, and when you ground something, just attach it to that. That will count as your ground, no need to solder it to the case!
NOTE: The second schematic is just how to wire the switches to the op amp, so you will still have to use the resistors from the first schematic. I made two different schematics because I knew people would want to use their own switch layout. This way they can see how the switches work.
For the 1/4" jacks, there should be two terminals coming off across from each other. If you look carefully, you can see that one is attached to the long contact while the other is attached to the entrance to the jack. Connect the one at the entrance to ground, and the other pin to where the schematic says (in=pin 2 out=pin 6)
Step 5: How to Solder
If you have never done something like this before, here are some tips that I learned to do (and not to do).
-Use a small piece of perf board. I fit this entire circuit (without the switches) onto about a 1X3 inch piece easily.
-Lay the circuit out on the piece like it is on the schematic. It will be reversed on the bottom, but I'm sure you can figure it out.
-When soldering, NEVER touch the solder to the soldering iron. Hold the iron to the wire and let it heat up. Then touch the solder to the wire, and let it be wicked up and down for a good connection.
-For this circuit, you can attach the terminals directly to each other instead of wiring a tiny gap. Just bend and solder. Be careful though!
-Attach all grounds to one copper wire soldered to the perf board. It makes everything ALOT easier.
-Make sure your grounds are connected very well or else you will get a loud buzz.
-Get some desoldering braid. That stuff is very useful! I couldn't have done this project without it.
Practice, practice, PRACTICE! The op amp can be cooked if you hold the iron on it for very long. Try cutting a little piece of perf board and solder wires to it and then desolder them. There is nothing worse than going through the entire process to find out the project doesn't work. I know. I did that twice (different designs).
Look at the second picture for what the soldering should look like.
Step 6: Connect Everything/the Box
Step 7: Making your own
Here is the simulator I used: http://www.falstad.com/circuit/. Let it launch and play around with it. If you want to import my design, press file>import, download the text file attached to this page, and enter the code from the file into the import box. You can then play around with it and see what the waves will look like coming out.
Play with the resistors, capacitors, and as many other things as you can think of. Since you know what clipping looks like in the wave, you know what to aim for. If you want others to look at your design before you build it, press file>export and copy and past the code into a comment below.
Some useful info:
-I suggest that you keep the input at 41 hertz because it is a note on the bass (a low E) and is easy to see because it is such a big wave.
-The average output for a bass or guitar is around .1-1 volts, so I used .325.
-The gain for the op amp is based on the resistor circuit underneath it. The actual equation for output voltage is Vin*(1+R2/R1). Since there are 4 of what would be R1, you would calculate the overall resistance, which is 133 ohms. R2 is 1K. R1s are all 100 ohms.
-The equation for resistors in series is R=R1+R2+R3 etc...
-The equation for resistors in parallel (like the 3 pictured on top of each other) is 1/(R1/1+R2/1+R3/1 etc...). In the case of this it is 33 ohms, then you add the 100 for the one resistor in series. That is 133.
-The LED should not go over 25 MW @ <2 volts or else it can explode. It smells really bad when it does.
-The LED must be at 15-20 MW to light up, and should not go over 2 volts.
If you do make one, though, post an instructable! Tell everyone how to made it, but it would be great if you could put a link back to this instructable if you used it much. Thanks!