#1
Ive been searching around and haven't been able to find a straight answer. It's about the output of a guitar. Does the guitar only output a voltage, or does it output a sine wave of a frequency of the note that is being played? For some background info, i'm making a guitar tuner for one of my classes. The main questions i am looking answers for is, what am i going to have to do to get the output of the guitar to become a frequency (maybe voltage-frequency converter), and how can i get the amplitude of the frequency to be between 0-5 volts? Thanks for any help
#2
I suggest you know some basic electronics / magnetics

Guitar outputs (on passive guitar) work through induction in the pick-ups. The vibrating of a metallic string over the magnets causes alternating current to flow. Naturally, the frequency of the current would be the same as that of the vibrating string.
I have no idea how active guitars work (might be the same, but amplified. Ask someone else about this), but their output has a frequency corresponding to the tone played as well, it's just louder.

I'm not sure about the output voltage. Passive guitars have an output measured in milli-volts I believe, so it's not much. Active guitars have a noticably higher output, but it's still not much.
Ask your teacher for help with amplifying the signal. It's not hard, but you'd have to learn how transistors work and that's just done a lot easier in real life

Good luck on your project
#3
It outputs a sine wave of whatever frequecies are being played. The voltage of this output is around 100 to 200 millivolts. A simple amplifier, like a 386 (0.5w op-amp) can get it to the voltage you may need.
#4
Quote by Tareqx2
Ive been searching around and haven't been able to find a straight answer. It's about the output of a guitar. Does the guitar only output a voltage,
It's not a DC voltage. It's an AC signal that changes in amplitude, frequency, and waveform.

Quote by Tareqx2
or does it output a sine wave of a frequency of the note that is being played?
Not a pure sine wave. Rather complex, due to harmonics on the string. And if more than one string is played at a time, things get REALLY complicated.

Quote by Tareqx2
For some background info, i'm making a guitar tuner for one of my classes. The main questions i am looking answers for is, what am i going to have to do to get the output of the guitar to become a frequency (maybe voltage-frequency converter),
No. V to F won't do what you're looking for. All you need is some signal conditioning to strip the harmonics from the guitar signal and give a constant amplitude to the AC signal.

Quote by Tareqx2
and how can i get the amplitude of the frequency to be between 0-5 volts? Thanks for any help
The amplitude of the signal will be around 100mV for most pickups. But that varies. Widely.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#5
Quote by SomeoneYouKnew
It's not a DC voltage. It's an AC signal that changes in amplitude, frequency, and waveform.

Not a pure sine wave. Rather complex, due to harmonics on the string. And if more than one string is played at a time, things get REALLY complicated.

No. V to F won't do what you're looking for. All you need is some signal conditioning to strip the harmonics from the guitar signal and give a constant amplitude to the AC signal.

The amplitude of the signal will be around 100mV for most pickups. But that varies. Widely.


Ok, so this is only going to be a really simple standard tuning guitar tuner. Assume only 1 string is played at a time. So will a simple amplifier get me a sine wave i can use to detect the frequency? what kind of filtering do i need to use and how can i get the amplitude constant from the ac signal?
#6
Quote by Tareqx2
Ok, so this is only going to be a really simple standard tuning guitar tuner. Assume only 1 string is played at a time. So will a simple amplifier get me a sine wave i can use to detect the frequency? what kind of filtering do i need to use and how can i get the amplitude constant from the ac signal?
Sine wave is probably not the best choice for detection of frequency. Maybe a square wave would be more useful. And easier to accomplish. Just lots of amplification so that the signal flattens out at the positive and negative supply rails. Then use a divide by 2 counter to make the duty cycle = 50%
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#7
Quote by SomeoneYouKnew
Sine wave is probably not the best choice for detection of frequency. Maybe a square wave would be more useful. And easier to accomplish. Just lots of amplification so that the signal flattens out at the positive and negative supply rails. Then use a divide by 2 counter to make the duty cycle = 50%


well, what i have right now is a program to time the rising/falling edges of a square wave to convert it to a frequency. I also tested this with a sine wave and the results are the same so either is acceptable. any links or tips on the amplification part? Is it just a simple op-amp?
#8
How i've looked at doing it with a microcontroller. This may be far beyond what you have thought about.

1. Amplify the signal so that it is large enough to be clipped on both sides by a diode.

2. Clip the top and bottom of the signal so that it is "essentially" a squarewave

3.Amplify the signal again and shift the signal by use of a clamping circuit so that you have it between 0 and 5 V

4. Use a free running timer that is set up for input capture and use that to determine the approximate frequency

5. From there you can program something to determine what note you have, or what note it is close to.
#9
Quote by XgamerGt04
How i've looked at doing it with a microcontroller. This may be far beyond what you have thought about.

1. Amplify the signal so that it is large enough to be clipped on both sides by a diode.

2. Clip the top and bottom of the signal so that it is "essentially" a squarewave

3.Amplify the signal again and shift the signal by use of a clamping circuit so that you have it between 0 and 5 V

4. Use a free running timer that is set up for input capture and use that to determine the approximate frequency

5. From there you can program something to determine what note you have, or what note it is close to.



well i have part 4 and 5... i just don't know how to do 1,2, or 3.
#10
For now look up

Op amp amplifiers
Diode Clipping Circuits
Diode Clamping Circuits

using those three you should be able to figure it out.

I could design it in about five minutes, but that wouldn't teach you anything. Take some time to look into the stuff and then you can ask me again later and i'll start to give you some pointers.
#11
Quote by XgamerGt04
For now look up

Op amp amplifiers
Diode Clipping Circuits
Diode Clamping Circuits

using those three you should be able to figure it out.

I could design it in about five minutes, but that wouldn't teach you anything. Take some time to look into the stuff and then you can ask me again later and i'll start to give you some pointers.


alright, i appreciate it. I'll take a look into that stuff. I have to get this project done by thursday so hopefully i'll be able to figure this out soon . Thanks for the tips though.
#12
Quote by Tareqx2
alright, i appreciate it. I'll take a look into that stuff. I have to get this project done by thursday so hopefully i'll be able to figure this out soon . Thanks for the tips though.


If you don't have it figured out towards the end of the day on tuesday feel free to ask again and i'll give you some more ideas. Its a pretty simple circuit really, the only problem is that its not gonna be exactly a square wave, but it should be amplified enough that it won't cause any problems counting the frequency.
#13
Quote by XgamerGt04
If you don't have it figured out towards the end of the day on tuesday feel free to ask again and i'll give you some more ideas. Its a pretty simple circuit really, the only problem is that its not gonna be exactly a square wave, but it should be amplified enough that it won't cause any problems counting the frequency.


Ok so i found some useful stuff for clipping and clamping the wave. But maybe i'm not getting this, but is the direct output from the guitar the frequency of the note? Some people have been saying it's a sine wave that directly represents the frequency, and others say it isn't. Keeping the amplitude the same is obviously not important, i just need the frequency intact to detect the falling edges. So do all i need to do is amplify it, clip it, and then clamp it?
#14
Quote by Tareqx2
Ok so i found some useful stuff for clipping and clamping the wave. But maybe i'm not getting this, but is the direct output from the guitar the frequency of the note? Some people have been saying it's a sine wave that directly represents the frequency, and others say it isn't. Keeping the amplitude the same is obviously not important, i just need the frequency intact to detect the falling edges. So do all i need to do is amplify it, clip it, and then clamp it?


The way i would do it is amplify it to something like a 3V peak to peak signal, assuming a 100 mV signal something like 30 times amplification would work..

Clip it in the upper and lower regions at 2.5V

"Clamp" it so that it varies from 0 V to 5V

This is somewhat assuming you get a simple sine wave out. It is possible to throw in more circuitry that will strip out the harmonics.

What you can do is determine the low and high frequency that you want to use and filter out all frequencies above and below
Last edited by XgamerGt04 at Nov 8, 2009,