Hello All,

I am designing a guitar tuner without the use of microchips. I have considered using the LM567 or NE567 chip but I am not sure if this is the most convenient approach. I know these chips are used for tone decoding for telephones and such but wondering if it is applicable in a guitar tuning circuit? Any help or suggestions would be greatly appreciated.

Thanks!

 

I am designing a guitar tuner without the use of microchips. I have considered using the LM567 or NE567 chip...

Huh? Are you or are you not using integrated circuits? Perhaps if you would explain your design goals more clearly. Like why you would avoid using the one technology that is right for the job.

 

Ya. Bad news. The LM567 is a microchip, and it is not the best tool for the job.
Google, "Guitar Tuner Schematic".

 

The LM567 is a microchip...

http://www.ti.com/product/lm567

Edit: Oh! I thought you meant Microchip!

 

Sorry guys,

I meant I will not be using a microprocessor because I have yet to take the class. Is there any other microchips that would be applicable besides the LM 567. From what I understand, Phase locked loop chips are the way to go without the use of a microprocessor. I'm hoping to input a guitar signal, amplify it with a lowpass opamp and design 6 LM567 chips to cover the six standard notes of a guitar. E a d g b e.

 

I think the more typical approach is to use a quartz crystal oscillator for a clock and then divide down to attain the needed frequencies. I suppose the clock speed must be chosen to have all 6 frequencies as factors so that you can divide by integers. (Just my speculation.) You don't need a separate circuit for each tone, just one adjustable circuit.

 

Unfortunately, the frequencies I need cannot be attained through dividing down 1 particular clock speed. THe frequencies needed are

• E4 ————- 1st———- 329.63Hz
• B3 ————- 2nd——— 246.94 Hz
• G3 ————- 3rd——— 196.00 Hz
• D3 ————- 4th——— 146.83 Hz
• A2 ————- 5th——— 110 Hz
• E2 ————- 6th——— 82.41 Hz

So, I may have to use one for each tone.​

 

Depends on what error you can tolerate.
A 1MHz crystal could do this:

MAIN-OSC= 1,000,000 Hz
FREQ..... DIV-BY ...ERROR %
329.63..... 3034.... 0.0097
246.94..... 4050.... 0.0107
196......... 5102... -0.0008
146.83..... 6811.... 0.0059
110.......... 9091.... 0.0010
82.41...... 12134.. -0.0037

A standard-frequency for sure, but those divisors would take some work

 

Unfortunately, the frequencies I need cannot be attained through dividing down 1 particular clock speed.

Nonsense. As demonstrated, you can get arbitrarily close by increasing the clock speed and the divisors.

Each half step (fret) multiplies frequency by the 12th root of two, so that you get a doubling of frequency over 12 half steps (an octave).

 

"arbitrarily close". That's what I call, "undetectably perfect". It means, no human, using only their senses, can tell the difference between this and perfect. Humans can't hear frequency to 5 digit accuracy.

Ask an old piano tuner. After starting with a tuning fork, they tune the piano by listening for the beat frequency of certain intervals. Reference, The Well Tempered Clavier. They are not using digital precision, they are using human senses, which actually don't respond well to the conception of perfection you have started with. To a musician, mathematically perfect pitch is a little bit discordant.

That being said, you can make 6 phase locked loops and use the error signal to drive an analog meter movement, if you want to. The LM567 has a temperature drift that will show up in the 4th digit. Six of them will require 90 ma, which is a difficult load for a 9 volt battery. I don't think you can get an analog error signal out of this chip. The output is just an on-off switch which can't be set closer than 3 digit accuracy or the musician will not be able to find it useful.

I think you can find phase locked loop chips that use a lot less current and have an analog difference signal that is accessible.

 

Or just do what the rest of the world does and use an app on your smartphone. If you're on stage, you already have a tuner anyway.

I'm not just joking. I've toyed around with every tuner app I can find and there are a LOT of differences. A very few I find are great but most border on unusable despite gorgeous displays and impressive capabilities. I'm biased towards the ones that allow rapid tuning under adverse conditions (like being on stage), so screen clarity and readability is a big factor.

My point is, the interface is a big deal. Just building the guts doesn't get you there.

 

How about the LMC 567 in terms of power supply current?

 

The LMC version uses a lot less power to do the same thing. It would be easier on us if you posted the datasheet yourself so we don't have to go poking around the internet to get what you already have in front of you.

 

Or just do what the rest of the world does and use an app on your smartphone. If you're on stage, you already have a tuner anyway.
...

Most decent guitar effects units these days have a tuner function built in too.

 

Most decent guitar effects units these days have a tuner function built in too.

I can remember when getting a guitar tuner was a "big deal". I had just one for years. Now I have several each on my computer, my laptop, my iPod and so on. Clocks and computers are cheap and ubiquitous.

Still, the interface is critical for usability and there's room for creativity of design.