=========================================================================== Digest of piezo pickup articles =========================================================================== From Jim_McGowan@qad.com Mon Nov 1 09:38:20 1993 Newsgroups: rec.music.makers.guitar.acoustic Subject: Homemade Acoustic Pickup Date: 31 Oct 1993 15:50:29 -0500 Organization: Johns Hopkins University (Homewood Academic Computing) ....................................................................... Item Subject: pickup.txt Please forgive the delay in posting these instructions -- a business trip came up out of nowhere after which I returned to find my home town on fire! Fortunately, everything's still here, including the guitars. Here's a topical question, at least for southern California netters: If you had 10 minutes to clear your personal belongings from your home, where would your guitars rank? ----------------------------cut here------------------------ Instructions for building your own piezo-electric pickup. Parts: Main parts are available from Radio Shack; the optional strap pin jack can probably be found at any decent guitar shop. I got mine for about $12.00 from McCabe's Guitars Shop in Santa Monica, CA. You'll need a soldering iron for the pickup wire and a drill with a quarter-inch bit (if memory serves) for the strap pin jack. Piezo Buzzer Element, Mini Part #273-064 Price: $1.79 Audio Cable; 2-Conductor, Shielded Part #278-514 Price $3.49/roll (you'll need about a foot of it) Preparation: None, other than to remove the strings from the guitar. Construction: The piezo element comes in a black plastic housing that must first be removed. Cut it away with a razor knife, being careful not to damage the element inside. Pry the element off the backing plate carefully -- it's held in with a bit of sticky glue. Do not bend the element! It consists of two thin layers of brass and ceramic that must remain bonded to one another for the pickup to work. Preparing the element: Once you have the element free of the housing, remove the little black and red leads with the soldering iron. These are not shielded and thus aren't of sufficient audio quality. Leave the two solder mounds on the element -- you'll re-attach the new wire to them. Sizing the piezo element: At this point you have a couple of options. The piezo element is a thin disc about the size of a quarter (sorry non-US residents, I can't think of an equivalent in your currency). I used the whole thing for my pickup, yet the original instructions in Frets magazine specifically pointed out that you can cut the element to any desired shape and size, provided that you are careful not to separate the layers of the element. A friend made one for his mandolin, cutting the element into a tiny rectangle. It worked great. (His pickup was external -- imagine trying to glue something inside a mandolin!) Whatever you decide on, try to retain the original solder points on the element. This will make attaching the new leads much easier. Attach the pickup wire: Solder on a length of shielded audio cable. The length depends on whether you want to mount the pickup internally or externally. If you decide on external, the length is irrelevant -- I suppose you could do like Barcus Berry with a two-foot length, at the end of which you could attach a 1/8" to 1/4" adapter jack. If you want an internal pickup, but don't want to drill a hole for the strap pin jack, there's no reason why you can't run the wire out of the soundhole. This looks pretty awful, but works just fine. For my internal pickup, I needed about 10 inches of wire. I doubt there's any electronic advantage to cutting the wire as short as possible, but then you don't want a lot of extra wire flopping around inside your guitar. Testing: Once the wire is soldered onto the element, test the pickup by jury- rigging the free wire end to a 1/4" jack and plugging into the nearest available amp. (Take all the necessary precautions regarding grounding, volume, etc.) All it takes are a few little taps of your finger on the element to see if it's live or not. If successful, proceed; if not, throw the whole thing away and start over. Attachment to the guitar: Let me preface this part with a warning: I'm no expert on pickup placement! I'm not an expert on anything to do with guitars, except drooling over them! I began by attaching the pickup externally with the stickum from my old Barcus Berry. I tried it on the guitar's face at several spots, but decided it sounded too "boomy". I settled on the treble side of the bridge, just where the B-B was mounted. Take your time here! I glued my pickup inside the guitar, approximating the location under the bridge. After much waffling over different adhesives, I settled on hot glue (the stuff that's applied with a little electric melting gun). I wanted something strong, yet not irreversible. That ruled out epoxy and crazy glue. The gum from the Barcus Berry always bothered me: too little and the pickup fell off, usually during a gig; too much and it muffled the sound. (What's needed here is a treatise on the sound-transmitting qualities of adhesives. I ain't your guy! Any acoustic engineers want to lend a hand?) I used only a single drop of hot glue, pressing the pickup into place and holding it for a minute or so. It's held perfectly for two years now. Strap pin jack: If you install a strap pin jack, be advised that, for structural and cosmetic reasons, it should go through the end block of the guitar, where there's usually a strap pin mounted with a small wood screw. I shall not lecture on the foolishness of mounting a jack elsewhere on the instrument. Using the hole from the original strap pin as a pilot, carefully drill a 1/4" hole as straight as possible through the end block. Perhaps you'll want to have this step performed by a skilled carpenter or luthier; I just winged it with the old Black and Decker and got good results. Very important! Feed the pickup wire through the jack's mounting nut and washer before threading it through the mounting hole. And why do you suppose I stress this point, hmmm? :-) Solder the pickup wire to the jack. I do not believe it matters which lead goes where. Again, an expert could tell you. Mount the jack and you're all done. Plug it in and let 'er rip. --------------------------notes-------------------------- I've found the quality of this home-brew pickup to be on par with that of the Barcus Berry that I'd used for years. It's a bit trebly, so I roll off the highs somewhat by running the guitar through a DOD stomp-box equalizer, or I request EQ through the PA if available. Perhaps a different adhesive would have rendered a better overall sound, but I'm very satisfied with the it nonetheless. I have experienced no problems with feedback, squealing, etc. Did I just get lucky? I installed this pickup on my trusty 1982 Yamaha L20A, a model that, despite being a fairly expensive, handmade axe, has no intrinsic collectable value. There is no visible clue to the existence of the pickup apart from the strap pin jack. --------------------------------------------------------------------------- From Jim_McGowan@qad.com Wed Nov 3 13:55:56 1993 Newsgroups: rec.music.makers.guitar.acoustic Subject: Re: Homemade Acoustic Pickup Organization: Johns Hopkins University (Homewood Academic Computing) Hi all, I thought I'd take a moment to correct and clarify a few things from my homemade pickup instructions posted earlier. 1. In the original post, I mentioned using a 1/4" (quarter-inch) drill bit for the strap pin jack. I re-examined the job I did and it seems I actually used a 3/8" bit. Sorry, I'm a lousy carpenter. 2. I forgot to mention that when attaching the pickup to the guitar, attach with the brass side of the element, not the ceramic side. Another poster pointed out that the Radio Shack Piezo Buzzer was not designed for musical applications -- I had hoped that was obvious. Sometimes you can get away with using something for other than its intended purpose and get good (though perhaps not spectacular) results. I'm sure the makers of Corecidin never intended their bottles to be used as slides either. My only real concern over posting these instructions is that someone might decide to install one in his/her 1942 Martin OO-28, but I believe the general IQ of our readership precludes that! And BTW, I'll take the sound of my pickup over an Ovation's anyday! (There... just had to say it!!) :-) - Jim McGowan jjm@qad.com --------------------------------------------------------------------------- Newsgroups: rec.music.makers.guitar.acoustic From: mib@bio128.uni-bielefeld.de (Michael Bruewer) Subject: Re: Homemade Acoustic Pickup Date: Wed, 3 Nov 1993 16:27:17 GMT Jim_McGowan@qad.com wrote: >> I used only a single drop of hot glue (to fix the piezo-element inside the guitar), pressing the pickup into place and holding it for a minute or so. << I had an old piezo beeper lying around and so I tried it yesterday. It works perfectly for me. In opposition to Jim I obtained the best result when fixing the *whole surface* of the element with hot glue to the inner side of the top under the bridge near the treble strings. The sound is very balanced and the output level much higher than the Barcus Berry. The noise is low, no feedback, it sounds like $200. Thanks for the advice. Michael Bruewer e-mail: mib@bio128.uni-bielefeld.de Uni Bielefeld Fak. Biologie/Abt.4 W-4800 Bielefeld 1 --------------------------------------------------------------------------- From: mitchell@panix.com (Paul Mitchell) Newsgroups: rec.music.makers.guitar.acoustic Subject: Re: Homemade Acoustic Pickup Date: 3 Nov 1993 17:58:51 -0500 Organization: PANIX Public Access Internet and Unix, NYC Radio Shack has a piezo element without the buzzer case. I think it is marketed as a PC speaker. It is probably identical, and will save the removal step. I have used these as MIDI triggers. BTW, GREAT IDEA!!! 8-}. -- Paul Evans Mitchell 212-858-1676 Follow your bliss. --------------------------------------------------------------------------- From: loredo@astrosun.TN.CORNELL.EDU (Tom Loredo) Newsgroups: rec.music.makers.guitar.acoustic Subject: Piezo info & sources Date: 3 Nov 1993 23:01:11 -0500 Organization: Johns Hopkins University (Homewood Academic Computing) Hi folks- Here's some info in response to the request about other piezo sources. I played with brewing my own piezo about 12 years ago, following the instructions of two columns by John Carruthers in *Guitar Player*, in the March 1981 (p. 96) and October 1981 (p. 136) issues. The unit he suggested was from Highland Electronics (2309 Santa Monica Blvd., Suite 178, Santa Monica, CA 90404), and was their Piezo Transducer Cat. #65. Each unit was $4.00 with $1.00 shipping. This was all back in 1981; for all I know the company doesn't even exist anymore. Perhaps our CA contributors can check on the company and the part. The pickup is *visually* very similar to what you find when you take apart a buzzer (but see below!). I was not very impressed with the sound when I experimented with it back then, but have since come to appreciate the crucial importance of using a high impedance buffer or preamp with piezo transducers (then I was just going straight into an amp). Even my fairly expensive L.R. Baggs saddle transducer (a much more recent aquisition!) sounds horrible going straight into the mixer on my Tascam Porta Two. It sounds fine if I buffer it with a DOD BiFet stomp box, though. This has gotten me interested in playing more with these pickups, so in a recent order of misc. electronics parts for a custom piezo preamp I'm working on, I also ordered a few extra bare piezo elements to play with. The supplier is All Electronics PO Box 567 Van Nuys, CA 91408 Order # (800) 826-5432 (Stores located in Los Angeles and Van Nuys) Their catalog is free. They are a fairly cheap surplus outlet. The piezos I bought were #PE-8, and cost a wopping $0.75 each. I haven't played with them yet, and can't vouch for their usefulness as guitar transducers. In any case, they are not listed in the current catalog; but two other bare piezo elements are: PE-12 (1.4 inch dia) and PE-14 (0.78 in dia). Both come with leads attached (the PE-8 and the Highland #65 require you to solder your own leads), and both cost $1.00 each. They also have lots of cheap buzzers you can take apart, if you want to go that route. However, they have a $10 minimum order, and a $4.00 shipping charge. Perhaps you could make up the difference by ordering coax cable and jacks, or parts to make your own hi impedance buffer.... Here are some remarks from Carruthers' article that may be of help: ********** Begin Exerpts ******** The piezo transducer used in the present example [the Highland #65] is a special unit selected for its sound quality, high output, and frequency response.... The diameter of the piezo determines its resonant peak. To obtain a good response, I selected a smaller unit, thus raising the peak [the Highland is slightly smaller than a nickle; this suggests the All Electronics PE-14 would be better than the PE-12]. It is necessary to use coaxial cable to connect the transducer to the amplification source... When connecting the hot, or center, lead to the piezo [ie, to the crystal itself, rather than the metal substrate], use the minimum amount of heat necessary to solder the connection. Presoldering (tinning) the lead will aid in this procedure.... Handle the piezoelectric transducer carefully. Damage to the crystal will affect its sound. Try not to flex or bend the device when applying or removing it [or prying it out of a buzzer!!], and dont't rip off the lead if resoldering is necessary. The location of the piezo on the instrument significantly affects the response in terms of both volume and frequency. It is therefore necessary to experiment on your instrument to obtain the optimum location of the unit. Use thin double-faced layout tape to apply the unit to various locations on your guitar. To improve sound reproduction, you can use more than one transducer. The wiring at the jack in this case would be as follows: All hots to common hot; all grounds to common ground.... Most piezos have limited output levels, and all share a common characteristic of extremely high output impedance. This latter characteristic causes high-frequency losses... [my experience, and most articles I've read, find instead a lack of warmth and excessive harshness].... The performance of the piezo we selected is less susceptible to these problems than are many commercially made devices. However, even its performance can be enhanced by the use of a preamp. The one I use has an extrememly high input impedance.... *********** End Exerpts *********** Hope this helps! Tom Loredo --------------------------------------------------------------------------- From: mpaul@unlinfo.unl.edu (marxhausen paul) Newsgroups: rec.music.makers.guitar.acoustic Subject: Piezo pickup project Date: 3 Jan 1994 03:16:05 GMT Organization: University of Nebraska--Lincoln 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 some columnist in Guitar Player 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. -- paul marxhausen .... ....... ............. ............ ............ .......... .. . . . . . university of nebraska - lincoln . . . .. . . .. . . . . . . . . . . . . . . . . . . . . . grace . . . . . . . . . . . . happens . --------------------------------------------------------------------------- From: paisley@exodus.exodus (Gary Paisley) Newsgroups: rec.music.makers.guitar.acoustic Subject: Piezo Film Sensors Date: 08 Mar 1994 14:25:24 GMT Organization: Schlumberger Laboratory for Computer Science For those of you who like to experiment with making your own acoustic transducers, here is the source for Kynar, a plastic film piezoelectric material: AMP Incorporated Piezo Film Sensors PO Box 799 Valley Forge, Pa 19403-2985 215 666 3500 I am in no way associated with this firm, but am responding to a request for the source of the material which I have used to make a variety of acoustic guitar, mandolin and bass transducers. Gary Paisley --------------------------------------------------------------------------- From: bsanders@ncsa.uiuc.edu (Barry Sanders) Newsgroups: rec.music.makers.builders Subject: Re: Scrap Materials = Instruments Followup-To: rec.music.makers.builders Date: 9 Mar 1994 22:15:36 GMT Organization: NCSA In article <2lg4o4$ff6@cat.cis.Brown.EDU>, plutchak@lager.geo.brown.edu (Joel Plutchak) wrote: > In article bsanders@ncsa.uiuc.edu (Barry Sanders) writes: > >Hi, > > > >I used to belong to several groups of experimental musicians that used > >all types of materials to make their music. It was great fun not > >only making the music, but finding the materials and inventing new > >uses for them. I see this as not only an inexpensive and rewarding > >musical hobby, but also as a perfectly valid way to re-use scrap > >materials. > > What about electrifying these instruments (Einst"urzende Neubauten > comes to mind, for some reason :)? Is there a standard way to amplify > or otherwise electronically warp the sounds, beyond simple miking? Yes, there is a cheap and relatively simple way to electrify most any vibrating instrument. Go to Radio Shack. Buy a piezoelectric buzzer, preferably the two-wire kind. Cut away the case. Solder the leads to a short piece of coax, terminated in a 1/8" phone jack. Mate this jack to a long piece of coax with a 1/8" phone plug on one end and a 1/4" phone plug on the other. Then, using either silicone rubber or plastic putty, stick the little piezo element to a vibrating part of your instrument. The 1/8" mini plug and jack are a sort of emergency stress relief mechanism in case you get too enthusiastic. You should attach the short piece of coax cable to the instrument somewhere, if possible. The 1/4" plug can be plugged straight into any microphone- level input on an amp, mixer or recorder. The piezo element provides a clean and flat signal. Try different locations on the instrument for different sounds. I've mic'd several acoustic instruments this way, and it works great! Beats spending hundreds of dollars on a Barcus-Berry contact mic. Also, I've never managed to saturate a piezo element, which is a constant problem with conventional mics. Hope this helps. Have fun with your instrument building projects! -Barry bsanders@ncsa.uiuc.edu --------------------------------------------------------------------------- From: sbaker@marimba.cse.tek.com (Scott Baker) Newsgroups: rec.music.makers.builders Subject: RE: Piezo pre-amp Date: 19 Oct 1994 16:50:42 GMT Organization: Tektronix, Inc., Beaverton, OR. Hi. A while back there was a discussion of preamps for piezo-type pickups. I recently built one which seems to work well. It is designed to have a high input impedance to match the output impedance of the pickup. The effect is to eliminate much of the "tinny" sound. I hope the following net list is decipherable. By the way did anyone read the article in EE Times Oct 3 issue on page 39 about creating tube amp characteristic with solid-state parts? PIEZO PRE-AMP PARTS LIST ------------------------ C1 .33uF C2 .33uF C4 .33uF R6 100K R1 10K R3 10M R4 10M C3 10UF R2 1K R5 1K D1 5.6V Zener D2 5.6V Zener U1 LF411 (National Semi) U2 TLE2426 (Texas Instruments) PIEZO PRE-AMP NET LIST ---------------------- NODE_1 R4.1 C1.1 U1.3 NODE_2 U1.6 R2.2 C2.1 NODE_3 C2.2 R6.2 R5.1 NODE_4 U1.2 R2.1 R1.2 NODE_5 D1.ANODE D2.ANODE NODE_6 U2.8 C4.1 NODENAME INPUT D1.CATHODE R3.2 C1.2 NODENAME OUTPUT R5.2 NODENAME +4.5V U2.3 R1.1 R4.2 NODENAME +9V C3.1 U2.1 U1.7 NODENAME GND C3.2 C4.2 U2.2 R3.1 D2.CATHODE R6.1 U1.4 Scott Baker sbaker@marimba.cse.tek.com ----------------------------------------------------------------------- | It's never too late for a happy childhood. -- Dr. Who | ----------------------------------------------------------------------- From sbaker@marimba.cse.tek.com Thu Oct 27 18:45:08 1994 From: sbaker@marimba.cse.tek.com (Scott Baker) Newsgroups: rec.music.makers.builders Subject: Re: Piezo pre-amp Date: 25 Oct 1994 17:34:21 GMT Organization: Tektronix, Inc., Beaverton, OR. Distribution: na NNTP-Posting-Host: marimba.cse.tek.com In Article 2173 of rec.music.makers.builders Dan Welter writes: >>I intend to build your preamp circuit for the Fishman piezo transcuders >>on my string bass and will post my findings. I was one of the ones who >>posted about sound quality problems when switching from pizz. to arco. >> >>First, I would consider the TLE2426 an exotic part. Is there an >>important reason to use it? I would prefer to use a thevin equivalent >>for R1 and R4, i.e. break R1 into two 20K resistors and R4 into two >>20M resistors to +9v and GND. With the exception of the TLE2426 I >>probably have everything on-hand. It's not essential to use the TLE2426. If you can't find one I would just create a 4.5V source with a couple of 10k resistors in series between 9V and ground and bypass the 4.5V node with a 10uF tantalum. The rest of the circuit remains the same. I would not recommend using 2 thevenin equivalents as you suggested as this would create 2 different bias voltages. For the piezo I used I had plenty of signal, so the gain of this preamp is (about) unity. If you need more gain, increase R2. The gain for this preamp is (R1+R2)/R1. Also please note I made a mistake on the original netlist that I posted. Pins 1 and 3 of the TLE2426 were swapped. Sorry about that. Good Luck! Scott Baker sbaker@marimba.cse.tek.com ----------------------------------------------------------------------- | It's never too late for a happy childhood. -- Dr. Who | ----------------------------------------------------------------------- --------------------------------------------------------------------------- From: berkwitz@blue.weeg.uiowa.edu (dan berkowitz) Newsgroups: rec.music.makers.builders Subject: Re: Preamp for piezo pickup Date: 16 Nov 1994 19:28:08 -0600 Organization: University of Iowa, Iowa City, IA, USA cwhitt@plato.ucs.mun.ca (Christopher Whitt) writes: >Dan Berkowitz>> What model number is the peizo buzzer you used? I >bought a buzzer from rat shack and fashion myself a pickup as well, but >the tone is really thin. I was hoping to experiement with multiple >transducer arrangements, different pickup placements. I think that >impedance may be my problem though, so I'd be interested in info on the >project you're referring to. I'm not sure of the model#, but it's the only one that costs $1.49 (at least in US$...it was also the cheapest). It was called a transducer rather than a buzzer, but I don't know if that makes any difference. Are you using this on an upright bass? That's my use, and it was also fairly thin and weak when it was on the lower middle of the bridge. Moving to the top of the bridge made quite a difference. The preamp I built was on p. 38 of the "Basic Semiconductor Circuits" version of the _Engineer's Mini-Notebook_. It's called "Basic FET Amplifier." I hope that helps. -Dan B. U of Iowa From Arsenio.Novo@mba.org Mon Jun 19 10:31:39 1995 Path: zip.eecs.umich.edu!newshost.marcam.com!usc!howland.reston.ans.net!agate!library.ucla.edu!unixg.ubc.ca!vanbc.wimsey.com!fonorola!Rezonet.net!nash.pubnix.net!mba!arsenio.novo From: Arsenio.Novo@mba.org (Arsenio Novo) Date: 18 Jun 95 15:24:41 Newsgroups: rec.music.makers.guitar Subject: Re: Piezo pickups/impedance question Message-ID: <14b_9506190558@mba.mba.org> Organization: MtlNet (MBA.org) MBA [514-465-8524] Brossard, QC Lines: 138 Mike Curtis said the following to All on the subject of Re: Piezo pickups/impedance question (17 Jun 95 19:24:28) MC> From: wd6ehr@kaiwan009.kaiwan.com (Mike Curtis) MC> Subject: Re: Piezo pickups/impedance question MC> : The piezo is generally lower output. Inputs on guitar amps are MC> fairly : high, usually around a meg or so. This is on the low side for MC> the : ideal piezo pickup but not to an extreme. MC> Most piezos require at least a meg. More is better. : >Should I: : > 1) Rig up some sort of impedance-matching transformer : > 2) Buy a small foot-pedal preamp : > 3) Both MC> : A transformer will not do it. A small FET-based or FET-opamp-based MC> : preamp is the way to go. Barcus Berry used to make these (not sure MC> : if they are still available). But most good electronics techs can MC> : work one up pretty quick. If possible, put the preamp close to the MC> : piezo. High impedances can be a source of hum. MC> You can also use a bipolar op amp in voltage follower configuration. MC> Another reason to have the preamp near the pickup is that coax has a MC> rather high interconductor capacitance, and with very high impedances, MC> you'll lose a lot of highs. MC> Mike Curtis MC> wd6ehr@kaiwan.com Hi, Your reply on built-in guitar preamps was most interesting. The simplest mod one can make is to simply buffer the output of the guitar. This is probably the most dramatically effective change one can make to benefit the sound. Cable capacitance severly affects the high end brightness. For jazz guitarists who run full bass tone on all the time it's a bonus but not for other guitar players. Usually a search for low capacitance cable leads one to some rather expensive wire! The biggest advantage of a driver is that the guitar sound no longer depends on the either the cable or the power amplifier's input circuitry. To wit, usually guitar cables are either microphonic to some extent or hum/noise prone too. This is exacerbated by the high output impedance of the typical guitar. Here's a very simple driver that can be built in under 1 hour: Guitar Output Cable Driver: - Ouput impedance is around 100 ohms and the gain is about -0.5 db. ______________________ | | | (+) Q1 | C1 +++++ --- 2N5434 | 100 uF [---] - B1 |---'d 16 wvdc | --- 9 volts Input o----+----| _|_ - Ouput ---- | g |-->. /// | ring _ >from R1 < s| + o-----------\/- | | jack 330K < +-----| [-----+-------o-----\/- | | wire < | C2 | tip J1 |_| _|_ < 1 uF < plug sleeve | /// R2 < 16 wvdc < R3 is on/off sw _|_ 10K < < 150K /// _|_ _|_ /// /// Parts list: C1: 1 x 100 uF 16wvdc, aluminium electrolytic capacitor. C2: 1 x 1 uF 16wvdc, dipped tantalum capacitor. R1: 1 x 330 K ohms 1/8 watt 5% metal film resistor. R2: 1 x 10 K ohms 1/8 watt 5% metal film resistor. R3: 1 x 150 K ohms 1/8 watt 5% metal film resistor. J1: 1 x 1/4" stereo phone socket, chassis mount. (if currently mono) Q1: 1 x 2N5434 low power switching JFET transistor. (Vp=2.5v Idss=100ma) B1: 1 x 9-volt battery. 1 x 9-volt battery connector 1 x 9-volt battery holder clip & 3/8" wood screw. 1 x 4" piece of thin flexible shielded wire. 1 x 1"x1" piece of perfboard, 3/8" wood screw & standoff. 1) Solder circuitry, 4" piece of shielded wire at R3 & solder battery connector positive wire, to perfboard. 2) Open guitar access cavity. 3) Remove the current socket. 4) Desolder wire & ground from socket. 5) Solder this wire to circuit board input at R1. 6) Mount battery holder & circuit on standoff inside guitar cavity. 7) Feed 4" thin coax through socket hole & solder to tip terminal. 8) Feed batt. connector neg. to socket & solder to ring terminal. 9) Mount socket, install battery in holder & close cavity. Mods: R1 can be increased to over 1 Meg or even omitted. The 330K value was chosen as a typical amplifier input impedance: adjust this value to suit your guitar. However, a larger value will tend defeat a guitar's bright switch. Notes: Since current consumption is very light a 9 volt alkaline battery will last & last & last... However, I've noticed that carbon batteries seem to make less internal noise than alkalines for some reason. In light of this experience a carbon battery might be a preferable & cheaper alternative. Arsenio arsenio.novo@mba.org ... Integrated Circuit (n): a device used to protect fuses. -- | InterNet: Arsenio.Novo@mba.org | Standard disclaimer: The views of this user are strictly their own.