Instructables

Very simple and cheap Guitar/Bass distortion pedal

Step 1: Find the parts!

Picture of Find the parts!
New circuit.png
Firstly, to make the pedal you obviously need the parts! Most of the parts can be found in the base of a CFL light bulb. I already had the parts to make this and have customised the parts to my liking. In the schematic, it says the input capacitor is 100n. It doesn't matter what value the input capacitor is really aslong as it is within the range of: 47n - 100uF. All the capacitors mainly do is affect the level of distortion at the output (as well as the diodes at the output!). For my transistor, I used a BC337 (On my old one) because I had it at the time but I'm sure that any NPN transistor will work fine. At the output stage, different kinds of diodes produce different levels of distortion. I used simple 1N4001 diodes (The most common diode around) But to get different kinds of output waves, many combinations of diodes exist such as schottky diodes (To produce a lower amplitude giving a nice germanium diode sound due to both germanium and schottky conducting at lower voltages) or rectifier and schottky diodes (Lopsided wave) etc. I tested the input down to 1.5v. at this voltage, it had some quite high distortion and a bit of an annoying hum but worked fine overall. Therefore, a 9v battery would last extremely long is the circuit works down to 1.5v.

The input and output capacitors depict the frequency response of the circuit e.g. The lower the input capacitor, the more bass is cut. This is good if your looking for a nice Trebly overdrive. Otherwise, this capacitor can be increased to any value. The values of these components doesn't particularly matter if your just looking for a simple distortion circuit.

The 100Ohm Resistor that is just above the Diodes can be removed to make the output wave much 'Harsher'.

The 100K resistor at the base of the Transistor mainly depicts the gain. Increasing this resistor increases the gain up to a certain point (It changed the bias of the transistor).

Edit: I have now included my new circuit diagram for the much more RAW! Distortion. Go to the last page for sound samples! Unfortunately, with this new circuit, the distortion isnt so epic at 1.5v :(

For this new circuit, i used a BC337-25, a much more gainier transistor.

 
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davidpaul233 years ago
1. Where do i place the volume and distortion pots in the schematics dude...? 2. Is that at the input before 100nF...?
pyrohaz (author)  davidpaul233 years ago
Sup dude, the volume pot would go from the emitter of the transistor to the 0v section, the value would need to be about 4.7k and a volume pot would be 100k in place of the 100k resistor and the wiper terminal on the pot is the output. Cheers :)
danymw4 years ago
where do you put the + and - of the battery?
pyrohaz (author)  danymw4 years ago
Do you mean on the schematic or breadboarding?:)
danymw pyrohaz4 years ago
I mean the schematic but I connected the - from battery to 0v. My board is complete now but I can barely hear any difference between the clean sound of guitar and distortion on. It's 100% correct unless there is a part (apart a wire) above the 2 diodes. (there's something? 100 near 2 bars,above the 2 diodes)
Thanks anyway,I'll try to put some heavy distortion.

pyrohaz (author)  danymw4 years ago
Hi, i have got to say, I designed this circuit a long long time ago lol, Its a bit crap tbh, When I get time, i will redesign a new one. What would be ideal is a high gain amplifier, giving a lot of signal for the diodes to clip. BUT ANYWAY! In most cases, this circuit will just pre-amplify your guitar signal a tad so that it may cause other pedals to overdrive sooner or adding a bit of character to other overdrive pedals. the 100 part is a 100R resistor, when designing it i had a bit of a misjudgement of the voltage coming out of the guitar going into the amplifier, if you get rid of this resistor, it should clip sooner causing a rougher sound. If your using a guitar, try and have it in "humbucking" position or if its single coil, try it using the neck and middle pickups humbucking or additional output. But in reply to your question, you did put the battery in the correct place. for further information, - normally signifies negative voltage, compared to 0v which is the same as "ground" :)
MrRodrigez4 years ago
hey, you think it would pay off to put in another circuit that has the same layout, but different config and a DPDT switch to have 2 different drives? I was thinking that would be pretty cool, but idk how much work would be involved..
pyrohaz (author)  MrRodrigez4 years ago
Hey, well that would be fine, for example, you could have the circuit above and a high treble circuit for two diff modes :)
sweet, ill try that after i get the time to finish the first one lol
hogge4 years ago
could I use a resistor with lower value instead of the 100k resistor after the input capacitor?
pyrohaz (author)  hogge4 years ago
That would reduce the gain significantly depending on the the value of the resistor, what is it?
hogge pyrohaz4 years ago
i have one that is 400 something ohm
pyrohaz (author)  hogge4 years ago
Yeeh, 400R isnt enough, you need atleast 82K ohm
hogge pyrohaz4 years ago
doh but thanks for a simple dist
made this and it worked very well, but it had an annoying buzz, but the weird part was it only buzzed when the strings weren't being strummed; when i strummed, it didn't buzz, but as soon as i muted the strungs, it would start buzzing. any suggestions? : )
and the thing with 3 wires coming from it, i think u said it was called a transistor. are those the the large rectangular things ive seen (and have a couple of) that are plastic at the bottom and metal at the top and have a hole at the top for a ground, or are they the things that are like black stubby cylinders with a flat part and are usually called Q1 or Q2 ?
pyrohaz (author)  bobbyderf1234 years ago
Well personally, i think the first thing you described was a capacitor (with the metal top). On the second part of your description your totally correct :) Yes, Q1 or Q2 is normally a transistor or 3 legged semiconductor :D
where it says 9-15v then 0v i assume thats just + and - ? im a beginer in electronics very nice instructable, very easy(which i like) because most other websites and instructables SAY they are very easy curcuits, but they dont look very easy to me
pyrohaz (author)  bobbyderf1234 years ago
Thank you! Yep, it works with any voltage below 15v and about 1.5v, its a quite versatile circuit
spenymoor4 years ago
is there some kind of variable capicator, and if there was would it be good to use it
that is not an accurate description of the capacitor's role in this circuit. The input capacitor value determines the amount of high/low frequencies that the pedal will pass. It has nothing to do with distortion. Otherwise, great article!
pyrohaz (author)  Barcode804 years ago
Hi, this was just a simple circuit (hence the name) for making some simple distortion, the input capacitor does affect the distortion because the bass notes cause the transistor to be 'overdriven' (High base voltage). Yes you are correct, the lower the capacitance, the less bass gets through but if you look at the tile, 0.1nF does work with a bass or standard guitar, thanks for the contribution though :)
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