Cheap Piezo Pickup For Acoustic Guitars (C) Paul Marxhausen, 1994 [This article has been produced for free distribution to individual readers on Internet newsgroups. Under no circumstances may it be reprinted in quantity in a commercial or non-profit publication of any kind without the written approval of the author.] I've posted this various places before but thought I'd do it again in connection with another do-it-yourself guitar project I've been working on, an internal acoustic guitar mike. This project is the "dollar pickup" for acoustic guitar, and all the credit for it belongs to a writer in Electronic Musician magazine, I think it was. I'm just passing it along. I disavow any responsibility for recommending it's suitability for any particular application. Many acoustic guitar pickups use some piece of piezoelectric material, a fancy name for a ceramic/crystalline stuff that generates electricity when flexed. Where can you get some? Well, many electronic widgets anymore use little piezoelectric beepers, which are little round brass discs with a thin layer of piezo material deposited on them, anywhere from about .25" to 1" in diameter. This is our key to a cheap pickup. I got a big bag of them from some electronic wholesaler, but you can run down to any Radio Shack(R) and get one. At RS they are usually in a black plastic case with a little hole in it for the sound to get out. PLEASE NOTE: you do NOT want spend extra bucks for a whole actual beeperwith the extra oscillator electronics to drive the disk into sound when it's powered. You're just after the raw disc. If it is in a plastic case, snip it out of there with an axe or snips or what have you. But be careful: the element itself will shatter if it is bent in any way at all. Remember, it's a slice of ceramic a fraction of a millimeter thick. Now you've got your element. If you're lucky, it may already have a couple of terminals or wires attached to it. If not, then the brass base is one electrode (I use it for ground) and the top of the piezo stuff is the other terminal. (Sometimes there's a little separate area of piezo, which is a feedback tab that we don't care about and won't use.) Soldering to the base and especially to the top is tricky: work fast, don't use more solder than you need. Scrape where you're going to solder very gently to get good solder adhesion. Radio Shack carries some very thin shielded microphone cable that's ideal for making a cable to your pickup. You can use a chunk of this long enough to get all the way to your amp, but a better approach is to use a short chunk that will go to a jack or other connector, maybe hanging on your strap, or to an endpin jack, etc. so you can plug a long, standard guitar cord to it. This way you can unplug more easily, or can make a permanent installation, and in any case help avoid the situation of tripping over the cord and having it rip the pickup off your guitar. Once you've got an audio cable and any connectors soldered on to your disk, you're set to mount it. How? You're faced with wanting to fasten it down as _tightly_ to the guitar as possible, but you probably don't want to permanently superglue it to anything right off the bat, so you have to compromise with your adhesives. Poster putty, wax, double-stick tape, etc. all have their advantages and drawbacks. I ended up using a Pritt glue-stick: it is waxy and allowed a solid, semi-permanent mounting on my bridge that I could still break free and scrape off without hurting the wood. Where to mount it? You can experiment, but you're probably going to want to have it in the close neighborhood of the bridge. My Alvarez has a two completely flat spots on each side of the bridge as part of the ornamentation, and I get the best sound and most low end on the bass side. If you're going to make this more permanent you could glue it to the underside of the top under the bridge. Also, just stuck to the top right next to the bridge isn't too bad. Once I had mine attached, I stuck a bit of felt over the top of it with glue because you will get an enormous HUMMMM if you touch it with your hand while you're amped up. This pickup can go directly to most high-impedance instrument amplifier or mixing board inputs with no additional preamplification; and I've stuck a Boss(R) flanging pedal in between with no ill effects. However, if you have a preamp of some sort, it's buffering will probably improve the low end response. How's it sound? Depends on your amp. Into my open-backed Peavey Studio Pro electric guitar amp, it sounds really awful. Into a Peavey KB100 keyboard amp with 15" woofer, good EQ, etc., it sounds just terrific. Like almost all piezo pickups, LOTS of treble and high end (every little squeak on the bass strings), a somewhat "brittle" sound. I bumped up the bass a bit, dialed up the spring reverb some, and sometimes kick in that flanger set for a chorusing effect. I think that some of the better of these disks I've assembled sound as good as inexpensive piezo-bridge-pickup-equipped guitars I've played in music stores. It's no Fishman Transducer...but then, it only costs a couple of bucks, and you can try sticking it _anything_: your violin bridge, your dulcimer top, your balalaika, etc. 14 March 1997 - A Web reader had the following comments on his own use of home-brew piezos: ==== From: To: Date sent: Tue, 11 Mar 1997 15:41:50 GMT Subject: FW: Pickups Found your stuff about piezo guitar pickups - I've been using these things for years! Here's some extra info from what I've learnt - feel free to add it, paraphrase or whatever - let me know if I can be of further help - publish my email address if required. Piezo elements - I buy mine in the UK from Maplin Electronics. I find these work best with the sound going through them; ideally one under each end of a (moveable) bridge - I've had excellent results with a mandolin & balalaika this way. I've tried them with violins, too; one under a bridge leg of an acoustic fiddle, a bit ropey though. This is because the output tone varies wildy with pressure; there's one particular level that gives a really good sound. I built an electric violin, and use a single element between the bridge feet; contact to the element is made by adjustable screws. This can sound great, especially when some else plays it ;-). The mandolin op is actually a bit bassy; great for small groups or single line playing but just adds lower middle mud with much else going on & chords. I have used the basic element-on-blutack method - I keep one in my PA kit for emergencies, but the sound is thin, as it relies only on the inertia of the element itself for mechanical vibration. You could try some weights on it? - but even so, not ideal in my experience. I have glued them inside acoustic guitars for a reasonable result, and even into the structure of a mandolin when I replaced the top on it. Um - well, makes a noise, but it was always a duff instrument anyway. Amplifiers - as you say, guitar amps are ropey - you need to bring down the presence/treble a lot to get any sort of sound, otherwise chords sound like a bag of nails. Acoustic-type amps or PAs are better. An inbuilt or belt-pack preamp is useful; I've used a TL072, first half as a high-impedance unity gain buffer, second half giving treble & bass controls, volume & out. Two outputs are useful, one to PA, one to a personal amplifier for monitoring. If building a belt-pack anyway, include a TDA7052(?) amp chip to give a headphone output, driving an in ear headphone, for example. If you don't want tone control, or use more op-amps, providing a balanced op to an XLR jack wins you friendship for life with sound engineers; they always have one DI Box too few! Digression - the TDA7052 speaker outputs are actually balanced w.r.t earth (obviously with a DC offset). Friends have reported using these to provide a balanced output, mainly with a condensor mic as a test box. Experiment away. I've also used condensor mics inside accordions; two or three under the cover above the keyboard, one or two in the bass end. These can all be connected in parallel, although separate outputs, or at least a volume control to drop the level of the bass end, is handy. A 9v battery is fairly essential; I have used 1.5v AA cells on their own, but the output gets distorted on the big squeezes, and anyway it fell out of it's clip too many times!. Again, an XLR output is useful. It's best to mount most of this stuff in a small metal box, fixed onto the accordion somewhere; depending on how precious the instrument is, everything can be taped on, with a dangling wire between bass & treble sides. I've hacked mine up a bit more; still with a screwed on metal box for connectors, battery and controls, but the mics are mounted internally, and I drilled a hole through the two 'bulkheads', fed a screened wire though the bellows for bass to treble connections. Makes life so much easier, and less frail. have fun _ I'll go & read the rest of your page now!