Quite a few people have approached me recently asking about how I got into electronics and, more specifically, building guitar effects pedals. So I decided to write this blog as some pointers on how to start out.
When you first start out, it’s very important to actually build circuits. You can support your experiments by reading up on the theory that accompanies the components and circuits you are using but nothing beats actually building the circuits … especially when you get them to work.
In order to quickly put circuits together you’ll need to have some prototyping equipment. I started out with the following gear…
- A multi-meter (£5-10)
- A Solderless Breadboard (£5-£25 depending on size)
- A battery clip (£1-1.50) & Battery (PP3 for most pedal circuits) (approx. £2)
- Some crocodile clips (£2-3)
- Some jump-cables/wiring kit (£15, or just buy some single core wire and cut to size yourself = cheaper)
- A small battery powered amp. (£15-£50)
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!
Once you have acquired your prototyping gear, you will need a handful of components to experiment with. When I first started out, this is the information I found the hardest to locate, there’s absolutely masses of info out there but knowing where to star really helps, so here’s some pointers…
In order to build and prototype basic circuits you need a basic understanding of the following components:
- Operational Amplifiers
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. and A.C. There’s more about that in the BASIC CIRCUITS section below.
Armed with knowledge of these, you can build most buffers, boosters, distortion, fuzz, overdrive pedals plus a few more, such as tremolos and phasers.
Now you need to know which components will be most useful in prototyping, so here’s a guide to commonly used components (information which I would have found invaluable when I started out)…
COMMON VALUES USED IN PROTOTYPING
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
Resistors and Capacitors
The easiest way to tackle these is to buy a “kit” of each component type, such as:
Non-Polarized Capacitors (film are arguable better for audio)
(bottom of page, there’s a kit of common values for £5)
http://www.rapidonline.com/Electronic-Components/Velleman-Electrolytic-Capacitor-Kit-120-Piece-13-0221 (around £8)
Some common values used in audio circuits…
- NPN Silicon Transistors
Very common: 2N3904, 2N2222A, 2N5088
Common: 2N3903, 2N2369A, 2N5089, 2N4401, MPSA18, MPSA13
- PNP Silicon Transistors
Very Common: 2N3906, 2N5087
- J-FET (Junction-Field Effect Transistors)
N-Channel’s: 2N5457, MPF102 and J201 (watch the pin out with the J201!)
- MOS-FET (Metal Oxide Semiconductor Field Effect Transistors)
(These are susceptible to static so be careful handling them.)
Silicon: 1N4148, 1N914 (Doesn’t matter which one, they’re both effectively the same)
L.E.D.s (Light Emitting Diodes)
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
You need to build these circuits, to really appreciate how the circuit works. So, get building! As long as you run from battery, the very worst you can do is pop or melt some components (we’ve all done it, it’s part of the learning curve).
One of the most basic circuits you can build is a transistor based buffer, here’s a great page, with a excellent explanation of how they work. The common values of transistors and OpAmp mentioned 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”…
Once you have mastered that, the next step is to try a Fuzz Face circuit, which is, arguably the most famous fuzz circuit, based around two transistors. Pay attention to the polarity of the voltage on these.
Next would be to build an OpAmp circuit, such as a booster. Here’s one with the appropriate maths to work out the gain…
So get building!