audio schematics for filters to isolate fundamental or harmonic tones?

You're playing only one note at a time, then?

1. Low pass (tracking) to take all the high off
2. High pass (tracking) to take the low off

(Tracking filters because of the possible range of notes you can get from a guitar covers about 4 octaves).

Not me. I suppose I could Google.

Bob

Use Cooledit to look at the FFT on the PC

A time-varying non-linear one, best I can tell.

You'll need DSP for this to have reasonable success. The math you're trying to emulate is quite non-trivial.

Best Regards,

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Do you have something against analog filters. The filters in the book I suggested are quite stable inexpensive and not too complicated.

Bob

You clearly didn't understand the application wrt guitars.

Graham

Thanks to everyone for your replies.

To clarify, the signal would only be from one string. Would that make it easier to build (such with an analog filter) ?

I love analog filters when they're appropriate solutions to the requirements.

Now, if you have an analog filter that'll satisfy these requirements, write it up in dissertation form, take a few classes, and a Ph.D. in Electrical Engineering is well within your grasp. Otherwise, I'll simply suggest that the requirements as stated are somewhere between "ill suited to analog" and "provably impossible in analog."

Best Regards,

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One string doesn't mean one frequency.

So no.

Graham

Pretty damn hairy even in DSP.

Graham

Band stop filter removes the fundamental, Band pass filter removes the harmonics. Q and band width determines how much. The filter suggested does either. You would need one for each string. You would need to combine the signals in a simple mixer circuit.

Bob

Same answer unless you isolate it to a single tone from that guitar string, which knocks out teh time-varying nature of it. If you get down ato a singel note, you can notch filter the hell out of somethign to try to remove the fundamental. And a low pass filter from hell could try to preserve the fundamental and kill everything else.

But playing a single note just isn't terribly musical.

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Amen.

The problem is that if you want to remove the harmonics well, you need a very sharp filter. If you had only a single note, you would tune the filter to put the cutoff just above the fundamental, so the 2nd harmonic would be well attenuated. You could select a suitable filter by consulting a filter design book, which shows the responses of various filter types and orders (at roughly 2 orders per op-amp stage). What you would quickly discover is that a really sharp cutoff requires a lot of stages, and the values of their components have to be really close tolerance.

But that's for a single, fixed-fundamental note. If you play another note into that same filter, the alignment won't be correct: If the new note is a bit lower, its 2nd harmonic will now fall in the passband of the filter. If the new note is higher, the fundamental will fall in the stopband.

Don't bother to think about trying to make the filter adjustable to somehow track the note being played: Such a many-stage filter with lots of critical components is really tough to adjust dynamically, but that's not the problem... it's figuring out what the fundamental is that you want to tune it to! This is called "pitch tracking" and it is a non-trivial problem. It's especially difficult for plucked strings like a guitar because the "2nd harmonic" is not exactly twice the fundamental, but moves around as the note attacks and decays. That means that the 2nd harmonic sort of "rolls through" the fundamental waveform, so simple schemes that look at waveform zero crossings get really confused.

Perhaps if you explain what your ultimate goal is, we can give better suggestions. But basically, you will need to use digital methods if you are serious about pitch extraction, and even then this is just "borderline" possible.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

I think the OP lilkes to play a bit with electronic music applications. It would not be that difficult to make a filter for each string, with a midi pickup. Getting satisfactory results with a normal pickup would probably be very difficult. moderate attenuation of the fundamental or harmonics is probably all he wants to do. The OP has been messing around with preamps a bit.

Bob

You don't know much about musical instruments do you ?

A single guitar string produces many notes.

Graham

A guitar string produces many notes.

Graham