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Double Bass DIY piezo?

ToneRanger

ToneRanger

Nov 2, 2004
554
29
Brisbane, Australia
#1
Has anyone tried making their own piezo pickup?

I'm currently designing an EUB - yesterday I was pricing hardware & pickups in music stores and found an acoustic guitar piezo bug for $20 (probably sells for about $3.75 in the USA). At that price I thought it was worth a try.
I stuck it on a bass - it sounded awful, with very low output.
Then I put it directly under a bridge - it had a huge output but very metallic tone.
Next, I got some cutters and hacked it out of its little metal case, so it was now just a little blob of plastic 1/8" thick - I put it under the bridge and it sounds amazing! Nice top-end clarity without being too edgy, huge output and solid, defined low end.

The instrument it's on is a one-string test-bed I made out of flooring timber to try some ideas and work out geometry before doing a serious EUB, but it's sounding so good I'm going to take it to rehearsal tomorrow and see how much fun I can have with just an A string!

I'd love to hear from anyone who's tried making or modifying piezos - I'm going to explore this option a little more before I buy a Fishman or Underwood.
 
#5
I have made my own piezo pick-up. I used a piezo buzzer from radio shack, the real small one. About 3\4". You just tear the thing apart and carefully unsolder the electronics and solder a ground wire to the outside ring and a positive wire to the inside part. I had a hard time keeping it all together. But it sounded fine when it was working. I dont think these high dollar piezo pup's sound any better then that ones at radio shack. It's all in the preamp. they just have nice molding that helps hold the wires in place.
 
#6
toonman said:
...I dont think these high dollar piezo pup's sound any better then that ones at radio shack. It's all in the preamp. they just have nice molding that helps hold the wires in place.
Click to expand...

I found some of those cheap piezo transducers today and made a pickup - I agree, it's no worse than some $200 products.
It needed some shielding to get rid of the hum, so I put insulation tape on the contacts and wrapped the whole thing in alfoil. Under the bridge it sound great - huge output (more than my active BG) without a preamp. Next step is to experiment with epoxy putty to make the wiring more durable.
 
#7
toonman said:
It's all in the preamp.
Click to expand...

Yep, the right (or wrong) preamp can make all the difference in the world. I'm not up on production units, though - I prefer to roll my own ;)

There's also the issue of down pressure. Too much and you end up "choking" the piezo. Although, installing under a bridge that needs to be cranked down pretty much means you get what you get and rely on the preamp to make up the difference.

Seeing that thread come up again gives me a warm fuzzy.
 
#9
bjornbass said:
what are piezos used for originally?
Click to expand...
The piezo-electric effect is the caracteristic of crystals to develop electrical charges when submitted to a mechanical constraint.
The reverse is also true. (piezo buzzers)
A piezo pickup therefore uses some crystals to produce output voltage from vibrations.
Piezos can also be used in industrial applications.
 
#10
Progress report on using piezo buzzers as pickups:

I'd had problems with hum, and with keeping the wires attached. Now I've got it licked:
I got a pair of the buzzers and carefully removed the brass disks from the plastic case. I then removed the leads and soldered one disk to the lightest shielded cable I could buy: inside +ve, outside -ve. On top of this I placed a thin sheet of cork, and then put the second disk on top. You can connect the second disk as a piezo but I found it doesn't make much difference whether you have one or two - I just use it for shielding by soldering a short wire from the top disk to the -ve.
So I have a brass sandwich, with the piezo well shielded inside and the cork providing a little flexibility. Now you could just wrap it all in insulation tape to hold it together - I put the whole thing inside heatshrink tubing to make in durable.

Under the bridge foot of my prototype EUB it's sounds wonderful - much louder than my BG pickups, a bright clear sound with solid lows and good dynamics.

I'm getting ripped off on the piezos - I have to pay a whole $3.95 each - but I'm pretty happy with the pickup.

Next project is to try some piezo film - I'm pretty sure this is exactly the same product used in some famous (= expensive) pickups:
Link Removed
 
#11
OK, some more progress - this time I've got a really nice pickup.

I bought a bunch of little MSI piezo films for $2 each from Windworld/Experimental Musical Instruments - Link Removed

Wired to some good Mogami cable they sound fine but there's a hum. The instructions that come with the pickups say you only need to shield the wiring, not the film, but that's not true! I tracked down some very thin copper foil with conductive adhesive (a 3M product) and covered both sides of the pickups, making sure the copper contacted the earth wire - they're now hum-free.

Next step was to get them to make good contact with the bass. I'm using a rough prototype solid-body EUB - I found the best position is under the bridge but slight movements of the bridge made dramatic changes to output. I solved this with some thin cork sheet - the sort of thing you use to make gaskets. A little of this under the pickup evens out the contact pressure, and also isolates some body noise (you probably wouldn't want to do this on an acoustic bass, but on a solid body it doesn't hurt to build in a little damping & flexibilty).

These pickups sound great! The piezo buzzers I used earlier have much higher output and don't need a preamp, but in comparison they have a more metallic sound.
I'm playing these film pickups through a Boss FA1 preamp into my Eden WT330/210XST and am very happy with the sound quality and dynamics - a very natural sound for a solid-body. I haven't found the need for eq aprt from rolling off some highs (I'll experiment with building a passive tone control into the pickup).

I've tried using just one under the E-string side of the bridge, and using a pair, one under each foot - both ways worked fine, but I think I'll stick with with the single because it gives the low end a little more prominence.

So for under $5 each (piezo film, copper foil, cable, plug) I've got a pickup that sounds as good as any commercial ones I've tried.
 
#12
ToneRanger said:
Next step was to get them to make good contact with the bass. I'm using a rough prototype solid-body EUB - I found the best position is under the bridge but slight movements of the bridge made dramatic changes to output. I solved this with some thin cork sheet - the sort of thing you use to make gaskets. A little of this under the pickup evens out the contact pressure, and also isolates some body noise (you probably wouldn't want to do this on an acoustic bass, but on a solid body it doesn't hurt to build in a little damping & flexibilty).
Click to expand...

I had this problem with one of my EUB's. The Piezo's were super finnicky. Slight movement = huge sound change. I found that the gasketing material helped me get a more constant sound as well, but it still wasn't exaclty what I wanted. I found out that the real problem was that my bridge feet weren't 100% flat/square. Once I made a new bridge with feet that had been jointed to make them flat and square, I found that it was much easier to get a good sound from the piezo's.
 
#13
Instead of hassling with solder, you can get conductive epoxy which has silver in it. Check it out: Invalid Link Removed


My piezo disks came from a medical supply house. They're apparently used as EKG sensors, or snore sensors, or something like that. They were dirt cheap I think, but someone gave me a dozen or so for free, better yet. :cool:

Oh, yeah: I've always just used Barcus-Berry acoustic putty for mounting the disks once I decide where I want 'em placed.
 
#14
finally a place for DIY piezo...
i just picked up a piece of piezo film (16mm x 73 x .2) from edmund scientific.com ($10) for a small scale fretless. it's just big enough to cover about a third of the bridge's baseplate. i want to install a small onboard preamp and wire up a volume control and nothing else. i've been told about the Kemo M040 and it looks promising. although, im a novice at wiring. these would be the parts: piezo, volume, preamp, battery, output jack. i know the piezo and output go on the ends but where would the other three go? any suggestions?
 
#15
nsagan01 said:
i want to install a small onboard preamp and wire up a volume control and nothing else. i've been told about the Kemo M040 and it looks promising. although, im a novice at wiring. these would be the parts: piezo, volume, preamp, battery, output jack. i know the piezo and output go on the ends but where would the other three go? any suggestions?
Click to expand...
Piezo -> preamp -> volume pot -> output

fdeck posted a design for a very simple DIY preamp buffer that I tried successfully - I think the thread is called 'DIY piezo preamp'.
 
#16
i came across the dtar volume and tone module. its visibility is what im going for but its FEASABILTY?
so it would be:
piezo---> kemo preamp/battery---> dtar volume and tone --->output jack.
??
and fdecks link isnt working properly for me...
 
#17
Here's the original preamp thread:
http://www.talkbass.com/forum/showthread.php?t=212647&highlight=how+preamp

Here's a current link to the preamp design:
http://www.talkbass.com/forum/showthread.php?t=212647&highlight=how+preamp

Note there's some discussion in the TB thread about alternate transistors that may work better and/or be easier to source. I found this little circuit was an excellent impedance buffer - it didn't add any gain (but my pickup already had plenty of level) but didn't add any noise either.
I tried a Kemo preamp but couldn't get it to work (although that's probably my fault).

The other preamp I tried sucessfully was Jack Orman's MosfetBooster. He sells good quality circuit boards that make DIY much easier. http://www.muzique.com/pcb.htm

Another budget basic preamp is available from Pickup the World, but I haven't tried this one: [Invalid or Expired Link Removed]
 
#18
I made a handful of piezo pickups using the film. So far I've had some problems with hum, lower output, and I found that it doesn't capture low frequencies as well as I like. The frequency range sounds great for cello, but it doesn't have enough bass frequencies.

Places where I could have gone wrong:
1) using cheap copper tape (I'm going to try using more of it, or switch to 3M)
2) using Invalid Link Removed jacks, and not shielding them as heavily as ToneRanger shielded his jacks
3)letting the film get too hot - there is a minor amount of delamination next to the contacts

I'm curious about using different kinds of films. Would a higher mass film give more lows?

I used Invalid Link Removed. Which seems identical to MSI's LDT0. I'm thinking of switching to films that come with either lead attachments or soldering pins w/ heatsinks to avoid delamination.
 
#19
Aaron said:
I made a handful of piezo pickups using the film. So far I've had some problems with hum, lower output, and I found that it doesn't capture low frequencies as well as I like. The frequency range sounds great for cello, but it doesn't have enough bass frequencies.

Places where I could have gone wrong:
1) using cheap copper tape (I'm going to try using more of it, or switch to 3M)
2) using Invalid Link Removed jacks, and not shielding them as heavily as ToneRanger shielded his jacks
3)letting the film get too hot - there is a minor amount of delamination next to the contacts

I'm curious about using different kinds of films. Would a higher mass film give more lows?

I used Invalid Link Removed. Which seems identical to MSI's LDT0. I'm thinking of switching to films that come with either lead attachments or soldering pins w/ heatsinks to avoid delamination.
Click to expand...

I found this pdf: http://www.contactmicrophones.com/techman.pdf

I'm a novice when it comes to electronics - so can anyone explain how capacitance will affect tone? I read that with higher capacitance a buffer might not be necessary - but if I use high capacitance tabs, with a 10 M ohm buffer, I would get even less low frequency roll off than lower capacitance with a 10 M Ohm buffer, right?

Also there is a figure (fig. 55 on page 47) recommending a fold over method for shielding piezo film for music applications. Would this work with laminated tabs?
 
#20
I have a homemade EUB with a radio shack pizeo.
I have an electronics surplus store in town and was able to experiment with a lot of different types and sizes elements and for whatever reason the radio shack 273-073 (I think it is) sounds the best.

My bass is a solid body with a solid bridge that rests on dense foam inside the bass. I think I'm close(r) to the swell and decay of an EUB than a lot of instruments.

I have the element dipped in plastic (the same stuff as tool handles use) and then lightly wrapped in copper tape as a shield.

I did notice that if I really smoothed the shielding it pinched the element and I didn't get any responce. I have it mounted on the top of the bridge (upper face) and it sounds really strong. After reading this thread I think I'm going to clamp it into position with a wooden caul, to allow some adjustability, and line it with the cork gasket as mentioned.

Thanks for the tip!
Rob Francis
 

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