The Radio Shack piezo is fine for a midi trigger, but isn't acoustically pleasing. I bought a dozen different types of piezos and have tried out as many designs to see how it all works out, and it wouldn't be worth it if I didn't really enjoy the effort. He's got $6-7 worth of wood there (it goes for $8-10 a board foot locally).Īnd you pay for the ease of just buying one and being ready to play, instead of messing around for a week to perfect it. That Sapele he's working with is not super-expensive wood, but it is a nice tonewood used for guitar backs. If you put in a filter you add another dollar, jacks are a buck a piece, etc. Cheaper if you go surplus and get lucky, but those are usually low output. Piezos, depending on what quality you go for, are from $3-10. It's not too much of a big deal to lose 20db as a good piezo overdrives the hi-z input on my preamps within the first couple of clicks of the trim, and provides plenty of power to drive a combo amp, so you really then have to decide whether you want all low-frequency so it sounds like a kick drum, or more high end content so it sounds more organic, like you're really stomping on a wooden stage or the back-porch of your farmhouse. In effect, it extends the low range and lowers the resonant peak so you get a wider range of frequencies at the expense of losing output - the more capacitance, the flatter the response and the more output lost. That resonant frequency might be 20db higher than all the of the frequencies it picks up, so the low-pass filter both rolls off excessive high end to help with microphonics, and adds enough capacitance to swamp the capacitance of the piezo. The problem with the cheap ones is that they have one resonant frequency, and it's high. And you can use larger piezos than under a bridge saddle, which are a lot more efficient. Making an under-saddle transducer do all of that means you end up with something that has to see a really high impedance load to get flat response across all frequencies.įor these tap boxes, you are looking for a narrower range, and less fidelity. The problem with acoustic guitar amplification is that you want it over a HUGE range of frequencies. If you get a good, high-output piezo, you get more than enough oomph without a preamp. Flat formats let you tap all over the top for different tones, but you have to lift your foot and stomp. Resonant side woods like a mahogany or spanish cedar will contribute some high end ringing, while less resonant woods will not contribute much.Īngling the front lets you tap it with your heel on the floor, but it's harder to build nicely and less versatile. A larger surface will ring nicely and produce a more organic thump as well as allowing you to kick over the pickup for a big boom, and near the corner for a light crack, like having your own floor-based cajon.ĭifferent wood, and thicknesses, make a huge difference. You pretty much get the big kick-drum tone from whacking the piezo, but there's no room on the top to let it ring or tap a corner and get a lower-volume and higher pitched tone. If you do build one, small boxes are easier to carry around, and far more durable for people who want to jump on them (as opposed to tapping them gently) but can't produce a lot of different tones. But it's mostly a matter of experimenting with capacitor values to match the tone you want and the output you expect. You can do the $1 piezo and it'll work, but if you shop around and get something with a useful resonant frequency and higher output, then smooth it with a pretty simple filter to widen the resonant sweet spot, it'll work better. Here starting at 1:30Īnyway, I read that and immediately invented a small box - then I searched the internet and found out that about a dozen people had invented it already. He said he put a piezo guitar pickup in the top of his pedal case and used it to make the thump. I got the idea from listening to Jeff Lang. I actually make boxes like this for people and sell them. ![]() There are dozens of cheap designs you can build, or many commercial products that fill this need. ![]() The electrical problem you'll need to solve is that the piezo pickup will need a preamp. ![]() ![]() (Edit: I'll take that back the grain suggests walnut or possibly mahogany) Hardwood would give a little more of a high frequency resonance to the thing and I bet that's something they didn't want. Good for making DIY drum triggers and so on.įrom the look of that knot in the pic, it's not even hardwood. I think I gave 15 cents for mine and I bought a small sack of them. If you shop online for electronics at all, most surplus places sell these piezo elements for way cheap. Most DIY articles online have you get a Radio S*ack part and pop the piezoelectric element out of it. Having done some DIY piezo stuff myself lately, I believe Scott has it exactly right.
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