# PVDF Piezo film for acoustic pickups



## gtract (Jan 18, 2008)

I've been fooling around with PVDF piezo film sensors, trying to build a decent acoustic pickup. The frequency response of this material is flat from a couple of hertz to over 2 gig, it has no self resonance, and sounds exactly like whatever it's attached to. Seems to have a lot of promise. Does anyone have any experience using this film?


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## Alain Moisan (Jan 16, 2010)

I don't have any experience with it, but I'm damn interested! Please tell me more!

Did you actually made the puickup yourself or you bought one that was made with PVDF? If you made it, how did you do this?


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## gtract (Jan 18, 2008)

Hi Alain. I used a Vibra tab, made by Measurement Specialties Inc. (Piezo Film Sensors), purchased from Mouser Electronics. (Mouser Electronics - Electronic Component Distributor), their part #
824-LDTM-028K. They cost about $2.00. There are other sizes available, up to large sheets, and the company will make any configuration; you can see them at MSI's site or at Experimental Musical Instruments (Experimental Musical Instruments ), who have very good information on applications and general usage. As far as actually making the pickup, it just has to be wired and shielded, and that's it. 

There's also a coaxial cable that has the PVDF material as the insulator. I'm pretty sure that it's the material used by Rick Turner for the D-Tar pickup, which is probably the best sounding saddle pickup I've heard. However, it's a coaxial cable mounted under the saddle, so the effects on the acoustic sound are quite noticeable. R. M. Mottola (Constructing an Under Saddle Transducer) has a great article on making a saddle pickup using the cable, and throws in a preamp design to boot! 

I've tried the pickup through the two commercial preamps that I own - a Baggs Dual Source and a Baggs Mixpro, and it works well with both. I've made a few preamps, based on JFETs, that seem to do a good job, as well. The tabs produce an extremely accurate picture of any of my guitars, including a spider bridge resonator (!), and just seem too good to be true. The material doesn't have as much output as a crystal piezo, so a good preamp is necessary - the Mixpro controls had to be turned up pretty high to get a usable signal - but they don't have the quack or that plastic sound that we all hate (except Nashville record producers!) . That's pretty much the only drawback that I've found. One post I saw said that David Enke of Pickup The World (Manufacturer of Acoustic Pickups for Acoustic and Electric Stringed Instruments and Drums) has developed a bridge pin containing the material, and that this one pin will give a full picture of the guitar's sound. Great guy, by the way, and he makes really nice pickups. 

Hope this helps. Feel free to contact me if I've left anything out. I'd be interested in hearing how it turns out for you if you decide to pursue it. Have fun!
Take care
Dave.


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## Alain Moisan (Jan 16, 2010)

*Cool!*

Thanks so much for this extremely detailed information, Dave!

I will most certainly try this out. I don't know when exactly but I can assure you that being able to offer my own pickup system to my customer is something that, as a guitar maker, I find quite attractive!

Thanks again! I will keep you updated (and quite probably will contact you a few times with questions!)


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## Alain Moisan (Jan 16, 2010)

Ok, first question: did you make a soundnoard transducer or an undersaddle transducer using the Vibra tab? 

The only image I found (from the catalog) looks too big to be used as an undersaddle transducer.


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## gtract (Jan 18, 2008)

Hi Alain. Soundboard. Placed by the x brace on the bridge plate. PUTW's placement guidelines work well. The tab not only picks up the top vibration, it also acts as a microphone, and gets some of the air. So, contact with braces, etc. should be avoided. The microphonic effect can be mitigated by using wire that has a plastic coating. I've tried using the tabs as they are and epoxied to slips of maple veneer, which seems to work well, and can be made into a pretty robust shielded pickup. Insulate the hot lead, shield the whole tab with aluminum foil (works as well as copper sheet in this application and it's much thinner and lighter) , and make the sandwich. If I were building I'd think about laminating the stuff into the bridge plate. (Easy for me to say - I don't have to pull the plate if I don't like it!). Right now I've got 2 tabs running into a JFET preamp, and the sound is quite impressive. At least as good as most pickups that I've used. I think the larger tabs would have higher output and a more complex sound. If you want a saddle pickup, the coax cable might be the best way to go. If you can get your hands on a Guild with the D-tar system installed you can hear it. Amplified sound is great, but the acoustic response is compromised. I haven't contacted MSI to get their rates on custom work with the sheet - might be worth a shot. Have fun.
Dave.


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## Alain Moisan (Jan 16, 2010)

gtract said:


> ... it also acts as a microphone, and gets some of the air.


Well that's the information I needed to confirm that it's not what I want! Most of my customers who want some pickup system intend to use it in a live performance environment, within a band. In such a case, a guitar with a soundboard transducer, as you pointed out, acts like a big microphone aimed at the monitor speakers, thus becomes a huge feedback generator!

But as you suggested, maybe I should try out their sheet material and make undersaddle pickups out of it. I'll first try some experimentation with the Vibra tap and see where this takes me.

Thanks again for your precious input and I'll let you know how it goes for me!


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## gtract (Jan 18, 2008)

Clarification: The microphonic effect I described is a very small component of the overall sound. While top-sensitive pickups are definitely more susceptible to feedback than saddle pickups, I haven't noticed unusual sensitivity on this rig, but I'm a solo instrumentalist, so my demands are different. That's really my focus on this - something that will get the real tone of the guitar out there, with as few tonal compromises as possible. After that, I'll tackle world hunger(!). Yes, band applications can be tricky. You might try contacting David Enke at PUTW. Great guy to deal with, and he knows more about this subject than I ever will, and seems to like a challenge. Also, if anyone's reading this that knows electronics, they might have some suggestions. I'm still at the basic guitar electronics stage, and most of my experiments so far are solder by number, as I once heard it put. Someone with electronics experience and knowledge might have something useful to add. Take care.
Dave
P.S - took a look at your site - nice looking guitars, great prices. You're using some gorgeous woods. Nice! Take care.


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## Alain Moisan (Jan 16, 2010)

gtract said:


> P.S - took a look at your site - nice looking guitars, great prices. You're using some gorgeous woods. Nice! Take care.


Thanks!

I don't have much time on my hands until next year, but I will most definitely make some experimentations with these sensors. Having the chance to make pickups for about 15$ just as good as what I would otherwise pay 150$ is quite appealing to me!

Good luck with world hunger, by the way!


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## stanb17 (Feb 12, 2011)

I find it fascinating that $25 in materials can be resold at nearly 10 times that cost.


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## Guest (Jul 20, 2012)

*How much should I shield...*



gtract said:


> Insulate the hot lead, shield the whole tab
> 
> 
> > I came across the forum and this exact question was on my mind! I'll be building two of these guys today.
> ...


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## Steve Works (Jan 16, 2014)

stanb17 said:


> I find it fascinating that $25 in materials can be resold at nearly 10 times that cost.


This is usually the case with any end-product that requires a lot of skill in manufacturing.
____________________________________________________________________________________________________
Steve Works
vibration measurement


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## The SaHrP (May 17, 2014)

Hi
I have experimented with the piezoelectric film on my homemade electro harp. 
I have also made a video on You Tube. Search in You Tube for; *Electroharp and drum hysj.* 
The video is 5.14 long. 
A *DT1-028K-L* piezofilm element under each string. A tiny saddle of bone between the string and piezofilm. Op amp buffer for each piezofilm. Divided into five octaves. Then summed into a 5 channel 19” mixer, I designed specific for the harps piezo system. Then some compressor, delay and reverb. The piezofilms are only for the first 33 harp strings. The lowest octave I use 4 P-bass magnetic mics. Next will be to implement this system onto a guitar.

The SaHrP


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