active filter for digital guitar tuner

[swh]

Hi every body i am building a digital guitar tuner.

and i face with a problem to remove the harmonics of the strings.
any idea?
thanks for your help.

 

[Agent 009]

Although under my nickname there's Master, I'm more newbie as you probably are, Man! But I have an idea: If you ever know the frequency of these harmonics, a simple frequency filter would erradicate these bad harmonics from the output sound!
If you really don't know what's the frequency, just use variable resistors and change their values accordingly. (For the circuit, I will try on my electric guitar to check for "normal" harmonics, and I'll try to sketch you a simple circuit...)

I hope that's helpful...

 

[grrr_arrghh]

similarly, despite my title, I prob don't know much more than you, however, I believe that you can use bandpass filters to filter out bad harmonics (a google search will help).

 

[k7elp60]

Well, I would determine the maximum frequency you want to hear then
calculate the values for this frequency as your cutoff frequency for an
active low pass filter, two two pole filters in cascade ought to do the trick.

 

[swh]

What you all said would be right if i want to remove only the harmonics of one string.But the big problem comes when i tried to eliminate the harmonics of all strings using only one filter.Those first hrmonics from the 6 strings of the guitar are different and i want to recover one of it when i plunk the coresponding string.

I would appriciate if you give me any idea.Thanks

 

[Nigel Goodwin]

Commercial guitar tuners are available at very little cost, I doubt they have any filtering for each string. What makes you think you are going to need to filter harmonics out?.

 

[Agent 009]

I think you can implement this filter-all-wanted-frequencies-out by using a THN Biquad filter, that is in the same time a Low/High/Band pass filter, and with variables resistors, you could just get from any part of the circuit the filter needed (actually, you'll get only three outputs, and I think guitars have 6 strings...)