Pedal Building.

A post which examines the electronic components, skills and knowledge required to build simple guitar effects pedals.

I often get approached by people asking me how to get started with audio electronics.  The best way is probably to build one of the excellent kits available from Fuzz Dog’s Pedal Parts or smilar websites.

However, in the age of the Maker, there’s nothing quite like building your own circuits from scratch.  Getting the basics down provides a good platform to try more complex builds later including etching your own circuit boards and designing custom enclosures.

Please note this post covers basic through-hole audio electronics for the hobbyists,  I’m sure there’s more professional level advise out there but, when it comes to electronics, I’m a hobbyist and happy to remain so.

The most important thing you can do, as a beginner, is actually build circuits. Sure you’ll fry a few compents but it’s all part of the  fun! Sure, you can (and should) support your experiments by reading up on the theory that accompanies the components and circuits, but nothing beats actually building circuits … especially when you get them to work.

In order to make the most out of your prototyping and development, you’ll need to buy some basic gear to build and test your circuitry.  None of these things are expensive but can help save you time and frustration in analysing and diagnosing any faults.

Multimeter

A multimeter for testing circuits

Jumpers

For connecting components

Battery Clip

For powering the breadboard

Crocodile

Crocodile/Aligator leads

Breadboard

For prototyping  circuits

Amp

For testing your circuits

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Safety: It’s important, when first starting out only to power your circuits with a battery, including the amplifier.  Thus, if you do make a mistake, like we all do occasionally, the worst you can do is pop a component or melt something! It’s a rite of passage in learning electronics.

Once you have collected all your prototyping gear togther, you will then need to purchase a handful of components to experiment with.  Sometimes it’s hard to ascertain which components are suitable for audio circuits, especailly when starting out.  Below are some common values of the most common through-hole components found in audio circuitry.

You’ll need to have a basic understanding of the following components to begin building circuits: Batteries (Cells), Resistors, Potentiometers (Pots), Capacitors (Caps), Operation Amplifiers (Op Amps), Transistors and Diodes.

With a good, sound knowledge of how these components operate, you can build most buffers, boosters, distortion, fuzz, overdrive pedals plus a few more, such as tremolos and phasers.

Remember audio is represented as A.C. (Alternating Current) in a circuit, so you need to know how these compenents work with both D.C. (Direct Current) and A.C.

Below are some of the most common values of components found in various audio circuits.  I compiled this info from building a variety of audio circuits.  However, having it in one place would have been invaluable when I first started my foray into audio electronics so, to save you some time, here they are…

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Transistors

Transistors come in all shapes and sizes from the simple BJT (Bipolar Junction Transistor) to the J-FET (Junction – Field Effect Transistor) and the MOS-FET (Metal Oxide Semiconductor – Feild Effect Transistor).  They also have polarity like diodes this is denoted as NPN (negative, Positive, Negative) or PNP (Positive, Negative, Positive).

Common Silicon BJT types:
NPN: 2N2904, 2N2222A, 2N5088, 2N3903, 2N2369A, 2N5089, 2N4401, MPSA18, MPSA13.
PNP: 2N3906, 2N5087, 2N2907.

Common J-FET types:
N-Channel: 2N5457, MPF102 and J201 (Note the pin out with the J201; it’s different!).

Common MOS-FET types:
N-Channel:
BS-170 (These are susceptible to static so be careful handling them).

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Capacitors

Theses can be divided into two groups, Polarized and Non-Polarized, of which, there are various types.  Arguably film are better for audio.

Non-Polarized Kit
Polarized Kit

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Diodes

Again there are various types made out of different materials such as Germanium.  However, Silicon are the most common: 1N4148, 1N914  it doesn’t matter which one, they’re both effectively the same.

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L.E.D.s

Another type of diode which is extremely common is the king that emits light, a.k.a. Light Emitting Diode.  These are, mainly, useful for two things; 1) telling if a pedal is engaged and, 2) using in place of a regular silicon diode for some interesting sounds.

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Resistors

The easiest way to tackle these is to buy a “kit” of values:

E12 Resistor Kit

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Potentiometers

Very common as a volume control: 100K-A (audio/Logarithmic taper).

Other common values: 470 or 500 ohms, 1K, 5K, 25K, 47K or 50K, 100K, 250K, 1M.

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Op Amps

Perhaps the most common of all is the 741 but a TL071 can be less noisy.  You can also get these in multiple OpAmp packages, e.g. the TL072 contains two OpAmps and the TL074 contains 4 OpAmps. Some less common values include the JRC4885D (Ibanez Tube Screamer) and the LM308 (ProCo RAT) although both are tricky to source these days.

I can’t stress this enough, you need to build circuits, using these components, to really appreciate how they work.  Providing you run from battery, the very worst you can do is melt or pop some components (we’ve all done it, it’s part of the learning curve).  Here are four basic links containing fairly simple circuits to build…

LM386 Amplifier

A Simple Power Amp is a great place to start and will save you money on buying a battery powered amplifier.  Note the LM386 is NOT an OpAmp, it’s a power amp in a chip

Fuzz Face

Once you have mastered that, the next step is to try a Fuzz Face circuit, which is, probably the most famous fuzz circuit.  It is based around two transistors but pay close attention to the polarity of the voltage on these; some are -9v (minus 9 volts) with a positive ground.

Transistor Buffers

One of the most basic circuits you can build is a Transistor Based Buffer, linked below is a great resource. The common values of transistors and OpAmp detailed above will work with all these buffers.  Pay close attention to the part about Vr, as most transistor (and OpAmp) circuits need to be “biased”

Op Amp Booster

Next you may decide to build an Op Amp Booster. Linked here is an example with the appropriate maths to work out the gain.

Electronics is a large field and, therefore, it’s not possble to cover everything in this initial post.  However, there should be enough information here to get you started building circuits and researching into how the components work within the field of small signal audio electronics.

Get building and share your thoughts and creations with us.

by | Dec 13, 2012 | Effects, Electronics, Tutorial | 0 comments

About the Author

Stuart Welsh

Stuart Welsh

Resident Audio Guru

Stu has been teaching Music Technology since 2002 at dBs Music where he is currently a degree Course Leader. He is an Avid Certified Expert Instructor in Pro Tools and holds a Masters Degree in Computer Music.

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