Arduino guitar effect

  1. How can i connect guitar (1/4 jack) to arduino?
  2. How can i manipulate the signal and how can i output the signal (1/4 jack)

You may not want to use the Arduino... It's analog-to-digital converter not quite fast enough for "CD quality" audio, and it's only 10-bits. And, there's no built-in digital-to-analog converter built-in, so you'd have to add an audio shield (an add-on audio board) for the output-side.

People have made guitar effect boxes with the Arduino, and you don't really need CD quality, especially if you are making distortion effects, but I'm just not sure....

  1. How can i connect guitar (1/4 jack) to arduino?

The Arduino can only handle signals between zero and +5V. Since audio signals are AC they go positive and negative and you generally need a [u]DC bias circuit[/u] (two equal-value resistors and a capacitor) to bias the input at 2.5V. Then, the Arduino can accept/read the negative half of the waveform, and you easily subtract-out the bias in software. (For a guitar pickup, your resistors should be 1 Megohm or more.)

A guitar can usually put-out about 1V with it's volume control cranked-up, so the signal level is about right for the Arduino (depending on how hard it's plucked/strummed and how "hot" the pickup is) and the Arduino itself has very-high input impedance (good for a guitar) before adding the bias resistors.

  1. How can i manipulate the signal and how can i output the signal (1/4 jack)

That's a "big question"... It depends on what kind of effect you want. Digital Signal Processing (DSP) is generally advanced computer programming.

If you are completely new to digital audio [u]this page[/u] shows how analog audio is sampled and how the analog waveform is recreated when you "connect the dots". If you understand that, you should be able to figure-out how to do simple things like change the volume (multiply or divide each sample by a fixed number), how to make a delay, and how to mix the delayed signal with the original for an echo effect (mixing is done by adding the data sample-by-sample.)

There is a [u]Free Online DSP Book[/u] if you want to get an idea of what's involved in DSP programming.

birkomester: 1. How can i connect guitar (1/4 jack) to arduino? 2. How can i manipulate the signal and how can i output the signal (1/4 jack)

See this page:- http://interface.khm.de/index.php/labor/experimente/arduino-realtime-audio-processing/

The scope for doing much processing is limited by the lack of memory on the Arduino. You can add extra SRAM or go to an Arduino that has more memory than the Uno.