Very simple and cheap Guitar/Bass distortion pedal

Hi there AmpBlaster.

I am very happy to answer any of your questions. Firstly, do you know the simple electronics knowledge about how transistors capacitors and resistors work? (Im taking it that you do :D).

Right i'll explain the schematic first so you can get to grips with that. In the schematic, the first section that i'll explain is the amplifying section. The transistor in this section is acting as an audio preamplifier, its based on a very simple audio amplifier circuit (miniscule amount of parts) The theory behind this form of amplifier (Class A) can be found all over the internet (I think it would save me typing it all out and repeating stuff, unless of course you want me to!)

The Audio enters through the capacitor (as you can see in the schematic. The input source is the AC wave within a circle, where it says input). it is going through a capacitor to allow the flow of the AC wave (input from guitar) and impede the flow of DC through the transistor. The 100k resistor biases the capacitor positive so the voltage is ~0.7v (The conducting voltage of a standard silicon transistor) The base has to be 0.7v higher than the emitter or it has nowhere to conduct to!

The 10k resistor (at the collector of the transistor) acts as a load resistor and as far as I know is just there to maintain the current between the base-emitter and collector-emitter. The lower this value, the lower base current required to maintain the gain. (this might be a tad to complex to understand lol but im sure you will :D)

Now, hopefully you understand that, if not just think of it as the 'amplifying stage'. After that, there is a capacitor to bias the DC meaning that when the input is 0v, even though on the positive side of the capacitor it may be ~8v, the output will be 0v. such as:

If the swing at the positive side of the capacitor was 0.5v such as: 7.4v to 7.9v, the output at the capacitor will be a 0.5v swing (0.5v to positive and 0.5v to negative). Since the conducting voltage of a silicon diode is 0.7v, the swing will need to be over 0.7v to 'clip' A clipped wave looks like a Sine wave, just with the tops chopped off so they look square-ish. the diodes clip the waveform by abruptly conducting straight to 0v. There are two diodes so they clip to 0v on the negative and positive sides.

I HOPE that has helped you :D any questions, ask away!

Hey, well that would be fine, for example, you could have the circuit above and a high treble circuit for two diff modes :)

Hey, all you need to do is connect the plus (red wire) to the 10k resistor, the ground (black wire) connects to the emiter of the resistor. :)

That would reduce the gain significantly depending on the the value of the resistor, what is it?

Yeeh, 400R isnt enough, you need atleast 82K ohm

Well, I just used an old instrument cable, chopped it in half and soldered solid core wire onto the engs and plugged them into the breadboard.

Another posibility, will just be to use standard 6.35mm Sockets and just plug them into the breadboard.

Thanks :D

Hey guys! Got some new pics, I recently made a new one! I will also include a sound track. Minor changes in the circuit:

*The input capacitor is now 10uF (To let through more bass) and the output capacitor is 22uF.

My new capacitors are now branded (Hitano) I would expect them to be high quality. (The producer even has a website!)

The Transistor is now a BC549C (Gain of ~500)

I didn't have a 100k Resistor so I used 2x 47K and 1x 22k resistors, this is equal to around ~120k

Same output diodes :)

Hey, is that a 2N3904? If so, it will work fine with it! The gain is pretty good for that transistor. To ground the circuit, just connect all the parts that are 0v or:
|
---
-

To the negative rail or 0v part of your power supply (Black wire)

For the diodes, aslong as there not LED's (The forward voltage is too high, they dont conduct at a low enough voltage) Any diode should work.

If you tell me all the components your using, I may be able to give you a hand :)

Ah hi there, It looks like you have got Zener diodes to me, don't quote me on that. I will have a go at drawing out the circuit in paint for you, I will upload it soon :)

Hi there, sorry its quite crude but i tried my best! Here it is:

Ah good! And its alright, thats what makes making an instructable so fun lol. What kind of power supply are you using? The power supply used can make a massive difference. I was originally using a mobile phone power supply (them cheapo £1.98 ones you can get off ebay!) and it produed a massive amount of hum, even when i wasn't playing! I did manage to make this better by putting some filter capacitors on the rails (plus and minus parts of the breadboard) As many as I could fit on! i think it was equivelant to around 2000uF, so that was an option. Another option would just be to try a new powersupply and make sure that all ground points are tied together!

Hmm, a battery shouldn't produce any hum theoretically, try a higher volatge battery first, if that doesnt work just try and double check that everything is grounded correctly. There the only things i can think of unless some of the components aren't funtioning correctly, have you tried the output without the diodes connected?

Hmm aw, im very sorry! it worked alright for me, if there is anything else you want, I will try as hard as poss to help

Ah, thats good news about the hum with your hand, You could try wrapping the whole circuit in cling film then in aluminium foil (the cling film will stop the aluminium foil shorting out the rest of the components. thats a cheaper way of doing the shielding, compared to using copper tape (in guitars)

I had another look on your breadboard and it looks like the + and - of the battery are on the same rail,this means the battery is shorting out! All you have to do is double check the battery. This should help.

Hey No worries:) Any questions, just ask

Hi there, When I get round to making it, I will upload some pictures, on the other hand, anybody else who has made this circuit and is willing to take a picture, i will happily add your picture to it :)

Owch! Have you connected the transistor the correct way round? Are the capacitors (If there the big capacitors with a negative stripe) connected the correct way round? Are the resistors in the correct place?

The Anode goes to positive, for the diodes, aslong as you connect them back to back (In other words, opposite to eachother) It should be ok! Test the capacitors and see if that works ok

Woo!! Well done! If you record some audio and youtube it, i will put it in the instructable it you want it to be :)

Hi there, Yes along as you get the Base, Emitter and Collector the correct way round, that should produce a nice distortion due to the high gain :)