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I recently started experimenting with DIY guitar pedals and I have been wanting to try to modify some of the schematics I have found, and eventually, design some of my own. I'm not an electrical engineer, but I have done a fair amount of circuit building/designing, however nothing having to do with an audio signal. I've been looking all over to try to find some resources on how different components affect an audio signal. Can anyone give me a run down, or know of any resources that might be helpful?

Thanks

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    \$\begingroup\$ This is too general of a question. The sound is not affected by individual components, but by blocks of components used together. A capacitor can have very different effects depending on the circuit it is used in. Do you have a specific sound you want to implement? \$\endgroup\$
    – endolith
    Commented May 23, 2011 at 14:25

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Instead of messing about with components, the modern way to modify sounds is in the digital domain, with digital signal processing (DSP). The audio is digitised by sampling with an ADC, modified with software running on a PC or DSP chip, and then converted back to analogue using a DAC. The ADC and DAC are usually combined in a codec chip.

An ideal device for experimenting with this technique is one of the Microchip 16-bit dsPICs. A few years ago I designed this low-cost audio processor based on one. It was intended for speech processing for amateur radio, but it would work equally well for guitar effects. PCB Gerber and drill files are available here, in the Files section. You need to join the group to access them.

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  • \$\begingroup\$ This is the best way to go, some of the analog components that were used in guitar petals are relatively difficult to source and/or are expensive as they are no longer manufactured. For instance bucket-brigade devices used for analog delays (echo type effects). \$\endgroup\$
    – Mark
    Commented May 27, 2011 at 14:46
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Sadly, most of the effects that have been made using analog components were done by playing. Basically someone sat there and switched components around until they got a "cool" effect. Many of these configurations were then patented and not tons published about them.

The best place to start is probably to learn about Op Amps. They are the building block for almost any type of analog signal processing. At first you will just be doing basic things like filters. Filters are like EQ. I bet you will be amazed at what you can do with very simple circuits.

You mentioned you have some schematics, learn what is actually going on with it. If you are confused and have the ability, you can come back here and ask what a particular block is doing. Once you learn what is going on in prior schematics, you might start getting some ideas of things to play with.

As @Leon Heller mentioned, DSP is where most of the market is going. DSP can be a much more difficult field to really understand, but if you have the will and desire, you should defiantly check it out.

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A tad off topic, but this helped me. I'm in the thick of building a mess of audio circuits for some kinetic art pieces. The question that I started with was similar to yours, but a little more basic: How does manipulating electricity make noise?

The two books that I refer to almost DAILY are Sound Synthesis: Analog and Digital Techniques by Terence Thomas and The Secrets of Analog and Digital Synthesis by Steve de Furia.

While both are geared toward building synthesizers, de Furia spends a LOT of time going through the bare essentials...like waveforms, how sound works, basic music theory about the relationship between tones on a scale, and then progresses to basic sound synthesis concepts. What's a ring modulator? How does an envelope work? What does an EQ do? The book goes into a lot of detail about what synthesizer components do to the sound.

Thomas' book is chock full of schematics, and for me, it built on de Furia's concepts. Once I understood what a white noise generator DID from de Furia, Thomas goes into the details about how to use specific resistors, caps and ICs to produce white, pink and brown noise.

I'm not sure if there's any crossover between synth-making and guitar pedals, but maybe there should be. :) The principles seem similar enough...make a sound, manipulate it and get another one.

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On the question of how different components affect an audio signal, the veteran audio engineer John Linsley Hood's books eg The Art of Linear Electronics, who has been designing amplifiers since the '60s, would be a good start. Chapter 2 goes through passive components in detail, Chapter 8 covers frequency modification circuits, there is a chapter on audio amplifiers and the pros and cons of different circuits including distortion. Noise and hum are covered in chapter 8, and you may find aspects of chapter 10 on low frequency oscillators and waveform generators relevant.

Whilst this doesn't give you circuits for deliberate distortion, many guitar effects also require/use dramatic levels of equiliser, and the chapter on amplifiers does cover valve configurations, so there is relevance to guitarists. I'd say overall it would give you a good grounding in the principles of analogue circuits so you can design your own with understanding rather than it being a receipe book.

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    \$\begingroup\$ I don't know this title, but audio books almost always focus on preserving the original signal as much as possible. I think OP is looking for distortion. \$\endgroup\$
    – stevenvh
    Commented May 23, 2011 at 9:49
  • \$\begingroup\$ What about it? We need some context for the link. Why is this resource helpful? \$\endgroup\$ Commented May 25, 2011 at 22:52

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