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[on:]

Hi! I took a 1/4" cable output from a guitar effect pedal, and I soldered wires to them. Now, I'm not sure if I need some transistors to hook it up to the arduino.
I need to connect the Arduino to my Guitar Amp with it.

Do I need any transistors so I can hook it up properly?

Also, Is there a way I can read the hertz of a note through the arduino?

Its for my project I'm working on.

[Reply #1 on:]

What are you trying to achieve with the Arduino?

[Reply #2 on:]

You seem confused as to what you want to do. Do you want to take the output of your effects peddle and connect it to the input of an arduino. If so use the circuit at the front of this circuit:-
http://interface.khm.de/index.php/labor/experimente/arduino-realtime-audio-processing/
Feed the back end to your amplifier.

[Reply #3 on:]

This is what I want to achieve.

So, the guitar player plays a note.
The Arduino reads the note, and finds the hertz of the note.
The arduino uses the hertz of that note, and finds the right tone to play, using the Tone Library

The only thing I need to do is to figure out how to read the note with the arduino.

I fixed the 1/4" cable, no transistors needed.

[Reply #4 on:]

Sorry but you will never achieve that. It is far too difficult to do with any processor let alone a low power one like an arduino. It will misidentify the notes.

[Reply #5 on:]

There has to be some way. It can misidentify notes, I don't care. I will delay it, but there has to be some way to read notes. Is there a library for reading notes?

[Reply #6 on:]

Is there a library for reading notes?

No,
if you want to try then look up the FFT.

[Reply #7 on:]

There has to be some way.

There is.  Pick the right hardware.  The Arduino is based on the ATmega328.  The ATmega328 is a microcontroller.  You are looking for a microprocessor. 

You are looking to do DSP (Digital Signal Processing) with your Arduino, which is a lousy platform for DSP.  From a hardware perspective 2k of SRAM just isn't enough even for what you are trying to do. 

You might want to look at something like the Maple platform (http://leaflabs.com/).  Similar to Arduino is concept but is based on a ARM 32-bit processor.

[Reply #8 on:]

Maybe adapt this for really small bands...

http://www.roguerobotics.com/wikidocs/projects/rmp3/spectrum_analyzer_demonstration

[Reply #9 on:]

A spectrum analyser or more powerful processor is not going to do it for you. There is no known commercial product that will do this well. Many try and do it imperfectly.

[Reply #10 on:]

Probably worth looking for some free software guitar-tuner and seeing how it does it.  It may be quite simple to do if you are prepared to wait a bit, harder to do quickly.  FFT is overkill when looking for one frequency, correlations and convolutions are the sort of technique to use and you only need 8-bit samples for this kind of task anyway.  For instance correlating with a chirp might yield useful results.

You will need a grounding in signal processing though...