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Good piezo pickup


erikbojerik

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Hi electronics experts

My son's science project (see here) is gathering some momentum, and we're now at the point of trying to select a proper piezo pickup to generate the response data. Here's what we'd like (probably asking for the moon here, but WTH):

1) flat frequency response over as wide a range as possible

2) one that couples very well with the wood (solid body)

3) one that can be removed easily and transferred from board to board

And, since we will continue to measure the frequency response of a few boards as they are fashioned into working bodies...

4) one that will work both with and without the strings attached

I realize that most (all?) peizo pickups use a pre-amp, but we don't want a preamp to color the frequency response data, so...

5) one that will work without a preamp

Are we asking too much? I hope not; your suggestions will be most welcome. :D

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I can't help you with pickup specs, but I can offer you a simple, inexpensive fixed-gain (ca. +26 dB) studio-quality preamp design with a frequency response curve <+/- .075 dB between 20Hz and 20 KHz - that should eliminate any problems with preamp coloration. You could simply compensate for the response of the piezo while you're compensating for the response of the driver - that might be easier, and offer you more options so far as pickups go. Best of luck, it sounds like an ambitious project.

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fixed-gain (ca. +26 dB) studio-quality preamp design with a frequency response curve <+/- .075 dB between 20Hz and 20 KHz

WOW! B) Those are some killer specs, I'm definitely interested!

You could simply compensate for the response of the piezo while you're compensating for the response of the driver

How do you mean exactly? (***Erik pictures 50-band EQ in the signal chain***) :D

Our intention is to use either pink or white noise as the sound source, from a speaker with a fairly flat response curve, and we've been worried all along about whether or not we could "subtract" out the response of the speaker+piezo system. To be able to do this would be a good thing, no question.

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Well, you can effectively compensate a speaker with a Zobel network, a simple resistor-capacitor series network in parallel with the voice coil, if you have the resistance and inductance of the speaker coil. As for the piezos, I haven't a clue as to their response, but it shouldn't be too hard to figure out using the same test gear you're using for the experiment, and once you've plotted a curve, compensation shouldn't be that difficult. Since these parameters won't ever change, you hardwire the filters into your test rig and forget about them. HTH.

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