Using a Teensy and a piezo to calculate the frequency of a guitar string

J

jbelardo01

New member
Hi folks,

I had an idea for a piezo style guitar pickup but that can be used on the individual strings of the guitar instead of being attached to the body. I was thinking that there could be some thin material that is attached to the piezo element and makes contact with the string as a way of detecting the string vibration and that would make it isolated from the body vibrations. From this it could go into the teensy and be able to calculate the frequency from the guitar string with the aim of having little to no latency.

Mainly just want to get an idea of if this is even a possibility and what kind of components could be used to test the circuit? I currently have a Teensy 4.0 that I can use.

Any help would be greatly appreciated :)
 
This is an acoustic guitar presumably? Don't think its going to work well as anything mechanically touching a string will damp it and probably buzz too. In an electric guitar the electromagnetic sensor exerts vanishingly small damping effect and having separate pickups per string is feasible.

Any any piezo element has inertia and will pick up the guitar body vibration if its attached to it.
 
There’s this … then you’d need a 6-channel piezo amplifier, and 6-channel ADC (probably TDM for Teensy, but you could do it with 3 audio adaptors, with a bit of work). I don’t know what the latency of the AudioAnalyzeNoteFrequency is like.

I’m sure cheap knockoffs are available, but do note if you use a piezo pickup it will need a piezo-specific amplifier.

To try stuff out I’d recommend you get an audio adaptor and try to make a monophonic system first. Then experiment with other pickups / amplifiers when you’re sure the basic concept is working.
 
MarkT said:
This is an acoustic guitar presumably? Don't think its going to work well as anything mechanically touching a string will damp it and probably buzz too. In an electric guitar the electromagnetic sensor exerts vanishingly small damping effect and having separate pickups per string is feasible.

Any any piezo element has inertia and will pick up the guitar body vibration if its attached to it.
Click to expand...
I was planning on doing it for electric since an acoustic will just vibrate too much, but was maybe planning on adding some rubber or keeping it floating from the body of the guitar to try and reduce the body vibration
 
h4yn0nnym0u5e said:
There’s this … then you’d need a 6-channel piezo amplifier, and 6-channel ADC (probably TDM for Teensy, but you could do it with 3 audio adaptors, with a bit of work). I don’t know what the latency of the AudioAnalyzeNoteFrequency is like.

I’m sure cheap knockoffs are available, but do note if you use a piezo pickup it will need a piezo-specific amplifier.

To try stuff out I’d recommend you get an audio adaptor and try to make a monophonic system first. Then experiment with other pickups / amplifiers when you’re sure the basic concept is working.
Click to expand...
yeah that makes sense, where could I find an audio adaptor that would work? and do you have any recommendations for amplifiers that work for piezo?
 
Your best bet is the official Teensy audio adaptor, easy to interface to your Teensy 4.0 as it’s designed specifically to do that. It has line in inputs, “just” connect to your electric guitar amp line level output … assuming you have one.

I Am Not A Guitarist - you can probably tell :), so no recommendations for piezo amplifiers. If you’re starting with an electric guitar, maybe a hexaphonic pickup would be a better route. I really don’t know…
 
Sure, if starting with an electric guitar and you’re not going to use it any other way. I suppose you could sum the 6 amp outputs for analogue use… But you still need a (different) 6-channel amp … and I couldn’t easily find a hexaphonic pickup, though I didn’t search for long.
 
There’s a function on the audio gui: https://www.pjrc.com/teensy/gui/?info=AudioAnalyzeNoteFrequency

I haven’t tried it but it’s somewhere down there on my to do list.

My BlackPearl pcb is a teensy 4.0 audio shield with a codec, a high impedance piezo buffer, and some other guitar centric features.

I’ve got piezo bridge saddle sensors from GraphTech on a few of my guitars. The sensors are embedded in some kind of slick material that they say saves string wear. I haven’t broken a string for a very long time, unless I was loosening them to swap pickguards, so it’s probably true.
 
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