Instructables

Simple overdrive effect pedal

This is a very simple overdrive effect. There are a lot of same kind of effects on the net, but I decided to design something simple. It's a great beginner project.

This is me playing with it:
http://youtube.com/watch?v=z-1BsJz9Cpk
First I play clean, the switch on the effect.
 
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Step 2: The schematic

Picture of The schematic
Now it's time to build one for yourself too!

This is what you need:

6.3mm stereo female jack
6.3mm mono female jack
DPDT switch
0.1uF capacitor
LM386 op-amp
220uF electrolytic capacitor
47k resistor
100k resistor
red LED
two 1N4148 diodes

Incase you don't know, how to read schematics, there are a plenty of tutorials available. Just Google
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Instead of 1N4148 diodes, could I use 1N5818 schotky diodes? and for the OP amp, should it be an LM386? Can't it be another op amp model?
I built the circuit and when I connect it to my guitar, I hear the radio! What did I do wrong?!!
I found that by connecting the diodes to the switch (top right point of the switch) rather than to ground, I get much more distortion. With the circuit as shown above, I get lots of overdrive, but hardly any distortion. Does that make sense?
Jahiruddin2 years ago
Dear
Thank you for provide this circuit diagram but now I like to test sound . Is it possible . Please help me.
Jahir
Jahiruddin2 years ago
Dear
Thank you for provide this circuit diagram but now I like to test sound . Is it possible . Please help me.
Jahir
666sebas9993 years ago
Does it need to be a LM386?
because i get a LM731 from an old recorder, can I use it too?
91chevywt4 years ago
Hey i've got a quick question for you. I've got everything together, as indicated in the diagram, and when I have it hooked up all switching the switch does is amplify the sound almost double. There is no distortion, just loud and clean. Do you have any idea what could be causing this? I checked my resistances with an ohmmeter and they seem to be in line with what the schematic calls for. Other than that i'm not sure what else to try.
Try pins 1 and 8.connect directly or put 10 uF capacitor between pins
ski4jesus3 years ago
Just so you know, on my LM386 amp, I have a 10uF capacitor between pin 1 and 8 with a switch and it gives off louder signal and tons of distortion, all the distortion you should need, but im going to try this anyway good job.
coolguy20153 years ago
will this work..
shmecker3 years ago
How about adding a 10uF capacitor between 1. pin and 8. pin for some more distortion? Also, adding a switch there is a good idea as far as I am concerned.
MGZero4 years ago
I'm curious as to why you have the clipping part in parallel rather than in series.  Wouldn't that cause a short circuit from the capacitor to the switch?  If that's the case then all of the current is going to bypass the diodes and such and then you won't get any distortion.  Can someone confirm this for me?
i think you are correct.
MGZero MGZero4 years ago
Nevermind, after doing some research on diodes, I understand what's going on here now.
-Syrus-4 years ago
How about connecting LM386's pin 1 & 8 together? This increases the gain, big time. More disto = more fun ;)
Schmidtn4 years ago
Maybe a silly question but, why is it a stereo input jack instead of a mono jack?  Though all guitars were single channel (but I don't know anything about making guitar pedals, so I'm asking). 
magnus0 (author)  Schmidtn4 years ago
 it's actually a power switch. when the input cable is plugged in, the power is turned on, if it's plugged out, it's turned off.
the guitar's mono plug will connect the ring and sleeve on the input plug, this will connect the power.
MGZero magnus04 years ago
That doesn't make sense.  Regardless of whether or not that is connected you're still going to have current draining from the battery through the op amp because of the ground.  The current is going to go through the op amp, drain to ground, and then return to the negative of the battery, which completes a circuit.  You sure this schematic is right?  I'm having quite a few problems with it.
kgyll4 years ago
 okay... how many volts of the 220uF electrolytic capacitor? and... 6.3mm stereo/mono female jack looks too small... reply to me ASAP
I think this is a great instructable!!!!  Although- the LED and Diodes section does not have any effect on the circuit....  you can disconnect them and the overdrive still works!!!!
Kin04 years ago
do you know how to wire DPDT switch the way he will bypass the battery will be off.
luudvig4 years ago
Hmmm... I only got amplified sound, no overdrive
adict12344 years ago
Sorry for a dumb question, but how do you ground this stuff? I mean what do you connect the ground units to?
every ground connection has to get connected to the negative battery end, everything with three lines (like a pyramid) all has to be connected together basically
Can someone write me schematic for volume pot or gain pot or both of them? Regrets and thanks!
could i use a tda2822 instead of the lm386?
Agroking5 years ago
Hey, Great instructable, But its not that hard to add a potentiometer right about here:
F0V3X4VFINO74G5.MEDIUM.jpg
sev7n Agroking5 years ago
How would you? Would you ground out one of the three parts that come of the pot?
Agroking sev7n5 years ago
of course, one of them is meant to be grounded anyway. That isn't affecting the volume of the output, its affecting the volumeof the input, i.e distortion (it is pre amp.)
sev7n Agroking5 years ago
WHat kind of pot would you use? I have a 10K and a 1M but i could get more from radioshack
reflecta5 years ago
maybe its more useful instructable with this i made it in paint :)
386 distotion son.jpg
AC DC5 years ago
im not good with scematics but i did understand evrything on it but not the input and output wiering, can you take a picture of them?
magnus0 (author)  AC DC5 years ago
i can't take a picture, because i don't have the pedal anymore. basically the input is a stereo plug and the output is a mono plug.
michoi5 years ago
sorry about the noobish question but what does ___ __ _
madragonn5 years ago
does it have to be the exact same model number diode or will any diode do ?
magnus0 (author)  madragonn5 years ago
any diodes will do, you will just get different sound
thanks :)<br/><br/>and another question, if I used a different Op Amp (for example this one <a rel="nofollow" href="http://commons.wikimedia.org/wiki/File:LM741_Pinout_Square.svg)">http://commons.wikimedia.org/wiki/File:LM741_Pinout_Square.svg)</a> but used the correct pinouts of the LM386 op amp to the pinouts of the LM741 op amp would this circuit still work, and would placing a variable resistor between the gain pins change the sound?<br/><br/>thanks again.<br/>
rkr5 years ago
I'm new to this, but I read up on how to read schematics and I still don't quite understand it, especially where the op-amp is. Any help?
pyrohaz rkr5 years ago
IF you look, the OP amp is the 8 pin chip in the middle. The LM386 is the op-amp, pin 2 (where the guitar signal goes in) is the - input (inverting inpit I think) while the Non inverting input it connected to 0v. All the circuit does is amplify the guitar signal and act like a schmitt trigger, which detects when the wave is positive and negative. When its positive, the output is high, when the wave is negative, the output is low. To get a negative voltage at the output, the OP-amp sinks and sources the capacitor then the clipping happens on the other side :) Hope it helps!
burgess.t25 years ago
i tried to make the footpedal, but nothing seemed to happen? should you solder the components to wires? or onto board? sorry i'm a noob at this sort of stuff but it seemed so interesting =D
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